js: use strict ... and fix the problems it points out

"use strict" gives stricter checks, both statically and at runtime. The
strictness tightens up the code and prevents some kinds of problems.

The <script> tag addition might not be pretty, but has consistently been added
with:

sed -i 's,<script>$,&'"'"'use strict'"'"';,g' `hg loc '*.html'`

codemirror: remove the bad and hopefully unused CodeMirror.modeURL guessing

It should always be set in initCodeMirror before CodeMirror actually is used.

javascript: added missing helper functions to make templates using codemirror work properly. (Issue #11)
* * *
imported patch codemirror-whitespacecleanup

codemirror: move everything to separate codemirror folder - splitting it up in css and js serves no purpose

- but it should perhaps not show up directly in /codemirror ...

Second step in two-part process to rename directories.
This is the actual directory rename.