Two factor authentication support (#630)

* Initial commit for 2FA support

Signed-off-by: Andrew <write@imaginarycode.com>

* Add vendored files

* Add missing depends

* A few clean ups

* Added improvements, proper encryption

* Better encryption key

* Simplify "key" generation

* Make 2FA enrollment page more robust

* Fix typo

* Rename twofa/2FA to TwoFactor

* UNIQUE INDEX -> UNIQUE

vendor/github.com/boombuler/barcode/barcode.go

@@ -0,0 +1,21 @@
+package barcode
+
+import "image"
+
+// Contains some meta information about a barcode
+type Metadata struct {
+	// the name of the barcode kind
+	CodeKind string
+	// contains 1 for 1D barcodes or 2 for 2D barcodes
+	Dimensions byte
+}
+
+// a rendered and encoded barcode
+type Barcode interface {
+	image.Image
+	// returns some meta information about the barcode
+	Metadata() Metadata
+	// the data that was encoded in this barcode
+	Content() string
+	CheckSum() int
+}