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/dockerfile/dockerfile.js

@@ -0,0 +1,79 @@
+// 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("../../addon/mode/simple"));
+  else if (typeof define == "function" && define.amd) // AMD
+    define(["../../lib/codemirror", "../../addon/mode/simple"], mod);
+  else // Plain browser env
+    mod(CodeMirror);
+})(function(CodeMirror) {
+  "use strict";
+
+  // Collect all Dockerfile directives
+  var instructions = ["from", "maintainer", "run", "cmd", "expose", "env",
+                      "add", "copy", "entrypoint", "volume", "user",
+                      "workdir", "onbuild"],
+      instructionRegex = "(" + instructions.join('|') + ")",
+      instructionOnlyLine = new RegExp(instructionRegex + "\\s*$", "i"),
+      instructionWithArguments = new RegExp(instructionRegex + "(\\s+)", "i");
+
+  CodeMirror.defineSimpleMode("dockerfile", {
+    start: [
+      // Block comment: This is a line starting with a comment
+      {
+        regex: /#.*$/,
+        token: "comment"
+      },
+      // Highlight an instruction without any arguments (for convenience)
+      {
+        regex: instructionOnlyLine,
+        token: "variable-2"
+      },
+      // Highlight an instruction followed by arguments
+      {
+        regex: instructionWithArguments,
+        token: ["variable-2", null],
+        next: "arguments"
+      },
+      {
+        regex: /./,
+        token: null
+      }
+    ],
+    arguments: [
+      {
+        // Line comment without instruction arguments is an error
+        regex: /#.*$/,
+        token: "error",
+        next: "start"
+      },
+      {
+        regex: /[^#]+\\$/,
+        token: null
+      },
+      {
+        // Match everything except for the inline comment
+        regex: /[^#]+/,
+        token: null,
+        next: "start"
+      },
+      {
+        regex: /$/,
+        token: null,
+        next: "start"
+      },
+      // Fail safe return to start
+      {
+        token: null,
+        next: "start"
+      }
+    ],
+      meta: {
+          lineComment: "#"
+      }
+  });
+
+  CodeMirror.defineMIME("text/x-dockerfile", "dockerfile");
+});