Preambles

CSS and JS preambles let you do some things more conveniently.
The CSS preamble could be used to define some classes for common elements.
The JS preamble could be used to set up things like dynamic graphs.
The JS preamble is called as soon as the question is created, before variables are randomised. You can wait for the 'question-html-attached' event to do things with the HTML.
Merge branch 'master' into preamble
apply preamble CSS to content areas
Merge branch 'master' into preamble
Merge branch 'preamble'
replace cleanJME binding with mathjaxHTML

Seems I missed some when I switched the non-editable content binding names!
use sstatic for cachebusting

the sstatic template tag adds a ?<last-modified-time> parameter to URLs, so browsers fetch a file when it's been changed, instead of using their cached copy.

Should prevent things like #194 from happening again.
add attribution for sstatic tag
Themes and locales have nice names now

Set in settings.py as doubles (nicename,code)
add other languages to settings.py.dist
add encoding line to settings.py.dist
max width on variable value cell

fixes #197
fix user profile form
catch unnamed parameters in custom function
new exams use user's preferred language

This also moves generation of the window.Editor object into the view, instead of the template
remove tags list from user profile

It takes a long time to compute, and I don't think it's ever used.
Update README.md

Add copyright notice
Merge branch 'master' into file-versions

Conflicts:
	editor/templates/editor.html