Update translations

* Pull from Pootle server
* Enabled ar and uk by default
White-space nits.
Removed a bunch of unused imports.
Ooops, class name is PootleJSONEncoder.
Fixed TemplateSyntaxError call.
Fix collectstatic for Django 1.4

Fixes bug 2752
Simplified unit filtering conditions.
Treat 'all' filter explicitly.
Documentation typos and improvements
Rename hook-examples to example-hooks
Comments typos