Updated codemirror to v4.12.

Did a lot of cleanup to limit the size of the plugin.
I kept the emmet plugin.

applications/admin/static/codemirror/addon/edit/trailingspace.js

@@ -1,3 +1,6 @@
+// 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"));