Big i18n tools update, I/II.

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-blender/trunk/blender@54809 954f8c5b-7b00-dc11-b283-0030488c597c