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/addon/mode/overlay.js

@@ -0,0 +1,85 @@
+// CodeMirror, copyright (c) by Marijn Haverbeke and others
+// Distributed under an MIT license: http://codemirror.net/LICENSE
+
+// Utility function that allows modes to be combined. The mode given
+// as the base argument takes care of most of the normal mode
+// functionality, but a second (typically simple) mode is used, which
+// can override the style of text. Both modes get to parse all of the
+// text, but when both assign a non-null style to a piece of code, the
+// overlay wins, unless the combine argument was true and not overridden,
+// or state.overlay.combineTokens was true, in which case the styles are
+// combined.
+
+(function(mod) {
+  if (typeof exports == "object" && typeof module == "object") // CommonJS
+    mod(require("../../lib/codemirror"));
+  else if (typeof define == "function" && define.amd) // AMD
+    define(["../../lib/codemirror"], mod);
+  else // Plain browser env
+    mod(CodeMirror);
+})(function(CodeMirror) {
+"use strict";
+
+CodeMirror.overlayMode = function(base, overlay, combine) {
+  return {
+    startState: function() {
+      return {
+        base: CodeMirror.startState(base),
+        overlay: CodeMirror.startState(overlay),
+        basePos: 0, baseCur: null,
+        overlayPos: 0, overlayCur: null,
+        streamSeen: null
+      };
+    },
+    copyState: function(state) {
+      return {
+        base: CodeMirror.copyState(base, state.base),
+        overlay: CodeMirror.copyState(overlay, state.overlay),
+        basePos: state.basePos, baseCur: null,
+        overlayPos: state.overlayPos, overlayCur: null
+      };
+    },
+
+    token: function(stream, state) {
+      if (stream != state.streamSeen ||
+          Math.min(state.basePos, state.overlayPos) < stream.start) {
+        state.streamSeen = stream;
+        state.basePos = state.overlayPos = stream.start;
+      }
+
+      if (stream.start == state.basePos) {
+        state.baseCur = base.token(stream, state.base);
+        state.basePos = stream.pos;
+      }
+      if (stream.start == state.overlayPos) {
+        stream.pos = stream.start;
+        state.overlayCur = overlay.token(stream, state.overlay);
+        state.overlayPos = stream.pos;
+      }
+      stream.pos = Math.min(state.basePos, state.overlayPos);
+
+      // state.overlay.combineTokens always takes precedence over combine,
+      // unless set to null
+      if (state.overlayCur == null) return state.baseCur;
+      else if (state.baseCur != null &&
+               state.overlay.combineTokens ||
+               combine && state.overlay.combineTokens == null)
+        return state.baseCur + " " + state.overlayCur;
+      else return state.overlayCur;
+    },
+
+    indent: base.indent && function(state, textAfter) {
+      return base.indent(state.base, textAfter);
+    },
+    electricChars: base.electricChars,
+
+    innerMode: function(state) { return {state: state.base, mode: base}; },
+
+    blankLine: function(state) {
+      if (base.blankLine) base.blankLine(state.base);
+      if (overlay.blankLine) overlay.blankLine(state.overlay);
+    }
+  };
+};
+
+});