Moved vendored js/css into public/vendor and documented sources (#1484) (#2241)

* Cleaning up public/ and documenting js/css libs.

This commit mostly addresses #1484 by moving vendor'ed plugins into a
vendor/ directory and documenting their upstream source and license in
vendor/librejs.html.

This also proves gitea is using only open source js/css libraries which
helps toward reaching #1524.

* Removing unused css file.

The version of this file in use is located at:
  vendor/plugins/highlight/github.css

* Cleaned up librejs.html and added javascript header

A SafeJS function was added to templates/helper.go to allow keeping
comments inside of javascript.

A javascript comment was added in the header of templates/base/head.tmpl
to mark all non-inline source as free.

The librejs.html file was updated to meet the current librejs spec. I
have now verified that the librejs plugin detects most of the scripts
included in gitea and suspect the non-free detections are the result of
a bug in the plugin. I believe this commit is enough to meet the C0.0
requirement of #1534.

* Updating SafeJS function per lint suggestion

* Added VERSIONS file, per request

public/vendor/plugins/codemirror/mode/dart/dart.js

@@ -0,0 +1,157 @@
+// CodeMirror, copyright (c) by Marijn Haverbeke and others
+// Distributed under an MIT license: http://codemirror.net/LICENSE
+
+(function(mod) {
+  if (typeof exports == "object" && typeof module == "object") // CommonJS
+    mod(require("../../lib/codemirror"), require("../clike/clike"));
+  else if (typeof define == "function" && define.amd) // AMD
+    define(["../../lib/codemirror", "../clike/clike"], mod);
+  else // Plain browser env
+    mod(CodeMirror);
+})(function(CodeMirror) {
+  "use strict";
+
+  var keywords = ("this super static final const abstract class extends external factory " +
+    "implements get native operator set typedef with enum throw rethrow " +
+    "assert break case continue default in return new deferred async await " +
+    "try catch finally do else for if switch while import library export " +
+    "part of show hide is as").split(" ");
+  var blockKeywords = "try catch finally do else for if switch while".split(" ");
+  var atoms = "true false null".split(" ");
+  var builtins = "void bool num int double dynamic var String".split(" ");
+
+  function set(words) {
+    var obj = {};
+    for (var i = 0; i < words.length; ++i) obj[words[i]] = true;
+    return obj;
+  }
+
+  function pushInterpolationStack(state) {
+    (state.interpolationStack || (state.interpolationStack = [])).push(state.tokenize);
+  }
+
+  function popInterpolationStack(state) {
+    return (state.interpolationStack || (state.interpolationStack = [])).pop();
+  }
+
+  function sizeInterpolationStack(state) {
+    return state.interpolationStack ? state.interpolationStack.length : 0;
+  }
+
+  CodeMirror.defineMIME("application/dart", {
+    name: "clike",
+    keywords: set(keywords),
+    blockKeywords: set(blockKeywords),
+    builtin: set(builtins),
+    atoms: set(atoms),
+    hooks: {
+      "@": function(stream) {
+        stream.eatWhile(/[\w\$_\.]/);
+        return "meta";
+      },
+
+      // custom string handling to deal with triple-quoted strings and string interpolation
+      "'": function(stream, state) {
+        return tokenString("'", stream, state, false);
+      },
+      "\"": function(stream, state) {
+        return tokenString("\"", stream, state, false);
+      },
+      "r": function(stream, state) {
+        var peek = stream.peek();
+        if (peek == "'" || peek == "\"") {
+          return tokenString(stream.next(), stream, state, true);
+        }
+        return false;
+      },
+
+      "}": function(_stream, state) {
+        // "}" is end of interpolation, if interpolation stack is non-empty
+        if (sizeInterpolationStack(state) > 0) {
+          state.tokenize = popInterpolationStack(state);
+          return null;
+        }
+        return false;
+      },
+
+      "/": function(stream, state) {
+        if (!stream.eat("*")) return false
+        state.tokenize = tokenNestedComment(1)
+        return state.tokenize(stream, state)
+      }
+    }
+  });
+
+  function tokenString(quote, stream, state, raw) {
+    var tripleQuoted = false;
+    if (stream.eat(quote)) {
+      if (stream.eat(quote)) tripleQuoted = true;
+      else return "string"; //empty string
+    }
+    function tokenStringHelper(stream, state) {
+      var escaped = false;
+      while (!stream.eol()) {
+        if (!raw && !escaped && stream.peek() == "$") {
+          pushInterpolationStack(state);
+          state.tokenize = tokenInterpolation;
+          return "string";
+        }
+        var next = stream.next();
+        if (next == quote && !escaped && (!tripleQuoted || stream.match(quote + quote))) {
+          state.tokenize = null;
+          break;
+        }
+        escaped = !raw && !escaped && next == "\\";
+      }
+      return "string";
+    }
+    state.tokenize = tokenStringHelper;
+    return tokenStringHelper(stream, state);
+  }
+
+  function tokenInterpolation(stream, state) {
+    stream.eat("$");
+    if (stream.eat("{")) {
+      // let clike handle the content of ${...},
+      // we take over again when "}" appears (see hooks).
+      state.tokenize = null;
+    } else {
+      state.tokenize = tokenInterpolationIdentifier;
+    }
+    return null;
+  }
+
+  function tokenInterpolationIdentifier(stream, state) {
+    stream.eatWhile(/[\w_]/);
+    state.tokenize = popInterpolationStack(state);
+    return "variable";
+  }
+
+  function tokenNestedComment(depth) {
+    return function (stream, state) {
+      var ch
+      while (ch = stream.next()) {
+        if (ch == "*" && stream.eat("/")) {
+          if (depth == 1) {
+            state.tokenize = null
+            break
+          } else {
+            state.tokenize = tokenNestedComment(depth - 1)
+            return state.tokenize(stream, state)
+          }
+        } else if (ch == "/" && stream.eat("*")) {
+          state.tokenize = tokenNestedComment(depth + 1)
+          return state.tokenize(stream, state)
+        }
+      }
+      return "comment"
+    }
+  }
+
+  CodeMirror.registerHelper("hintWords", "application/dart", keywords.concat(atoms).concat(builtins));
+
+  // This is needed to make loading through meta.js work.
+  CodeMirror.defineMode("dart", function(conf) {
+    return CodeMirror.getMode(conf, "application/dart");
+  }, "clike");
+});

public/vendor/plugins/codemirror/mode/dart/index.html

@@ -0,0 +1,71 @@
+<!doctype html>
+
+<title>CodeMirror: Dart mode</title>
+<meta charset="utf-8"/>
+<link rel=stylesheet href="../../doc/docs.css">
+<link rel="stylesheet" href="../../lib/codemirror.css">
+<script src="../../lib/codemirror.js"></script>
+<script src="../clike/clike.js"></script>
+<script src="dart.js"></script>
+<style>.CodeMirror {border: 1px solid #dee;}</style>
+<div id=nav>
+  <a href="http://codemirror.net"><h1>CodeMirror</h1><img id=logo src="../../doc/logo.png"></a>
+
+  <ul>
+    <li><a href="../../index.html">Home</a>
+    <li><a href="../../doc/manual.html">Manual</a>
+    <li><a href="https://github.com/codemirror/codemirror">Code</a>
+  </ul>
+  <ul>
+    <li><a href="../index.html">Language modes</a>
+    <li><a class=active href="#">Dart</a>
+  </ul>
+</div>
+
+<article>
+<h2>Dart mode</h2>
+<form>
+<textarea id="code" name="code">
+import 'dart:math' show Random;
+
+void main() {
+  print(new Die(n: 12).roll());
+}
+
+// Define a class.
+class Die {
+  // Define a class variable.
+  static Random shaker = new Random();
+
+  // Define instance variables.
+  int sides, value;
+
+  // Define a method using shorthand syntax.
+  String toString() => '$value';
+
+  // Define a constructor.
+  Die({int n: 6}) {
+    if (4 <= n && n <= 20) {
+      sides = n;
+    } else {
+      // Support for errors and exceptions.
+      throw new ArgumentError(/* */);
+    }
+  }
+
+  // Define an instance method.
+  int roll() {
+    return value = shaker.nextInt(sides) + 1;
+  }
+}
+</textarea>
+</form>
+
+<script>
+  var editor = CodeMirror.fromTextArea(document.getElementById("code"), {
+    lineNumbers: true,
+    mode: "application/dart"
+  });
+</script>
+
+</article>