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/theme/mdn-like.css

@@ -1,13 +1,13 @@
 /*
   MDN-LIKE Theme - Mozilla
   Ported to CodeMirror by Peter Kroon <plakroon@gmail.com>
-  Report bugs/issues here: https://github.com/marijnh/CodeMirror/issues
+  Report bugs/issues here: https://github.com/codemirror/CodeMirror/issues
   GitHub: @peterkroon
 
   The mdn-like theme is inspired on the displayed code examples at: https://developer.mozilla.org/en-US/docs/Web/CSS/animation
 
 */
-.cm-s-mdn-like.CodeMirror { color: #999; font-family: monospace; background-color: #fff; }
+.cm-s-mdn-like.CodeMirror { color: #999; background-color: #fff; }
 .cm-s-mdn-like .CodeMirror-selected { background: #cfc !important; }
 
 .cm-s-mdn-like .CodeMirror-gutters { background: #f8f8f8; border-left: 6px solid rgba(0,83,159,0.65); color: #333; }