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/haskell-literate/haskell-literate.js

@@ -0,0 +1,43 @@
+// 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("../haskell/haskell"))
+  else if (typeof define == "function" && define.amd) // AMD
+    define(["../../lib/codemirror", "../haskell/haskell"], mod)
+  else // Plain browser env
+    mod(CodeMirror)
+})(function (CodeMirror) {
+  "use strict"
+
+  CodeMirror.defineMode("haskell-literate", function (config, parserConfig) {
+    var baseMode = CodeMirror.getMode(config, (parserConfig && parserConfig.base) || "haskell")
+
+    return {
+      startState: function () {
+        return {
+          inCode: false,
+          baseState: CodeMirror.startState(baseMode)
+        }
+      },
+      token: function (stream, state) {
+        if (stream.sol()) {
+          if (state.inCode = stream.eat(">"))
+            return "meta"
+        }
+        if (state.inCode) {
+          return baseMode.token(stream, state.baseState)
+        } else {
+          stream.skipToEnd()
+          return "comment"
+        }
+      },
+      innerMode: function (state) {
+        return state.inCode ? {state: state.baseState, mode: baseMode} : null
+      }
+    }
+  }, "haskell")
+
+  CodeMirror.defineMIME("text/x-literate-haskell", "haskell-literate")
+});