Big i18n tools update, II/II.

Now everything should be done with ui_translate addon (which is also now fully functional again, in theory ;) ).

Notes:
* Everything is still a bit raw and sometimes hackish.
* Not every feature implemented yet.
* A bunch of cleanup is still needed.
* Doc needs to be updated too!

git-svn-id: https://svn.blender.org/svnroot/bf-extensions/trunk/py/scripts/addons@4323 96b784f8-4ae3-dd11-aff7-0030488c597c