First stab at scrolly checkbox lists
Remove extra ul/li from nested checkboxes
HTML improvements

- Swap out legend tag which wasn't behaving in ie
- Tag controls
- Add open class to facet for testing
Tidy CSS. IE6 improvements. Finish off styling

- Style controls
- Improve for ie6
- Tidy ordering
Sprite for scrolly checkbox arrows
Correct checkbox id
Add full ul/li to checkbox list

Added full ul/li back to allow semantically correct nesting (useful for javascript checking/unchecking of nested checkboxes).
I know uls/li used in this way lead to additional (and unhelpful) screen reader chatter, can't think of a better way at the moment but if you can PLEASE TELL ME.
Initial go at checkbox behaviours

- Probably doesn't want to go in application.js ultimately
- Needs ie6 exclusion
- Needs all the other stuff that whitehall has.
Add clickable div for opening facet
Fix .open change for dropdown
IE6 fixes
Cursor pointer for clickable facet
Restructure js and move to separate files

- JS now uses the constructor pattern as described in https://github.com/alphagov/whitehall/blob/master/docs/javascript.md.
- Added proxifier so `this` still works
Finish js rewrite
Set up ie stylesheets
IE6 fix for label width