LUN-1413: Change site_url get_choices.
LUN-1413: Cleanup.
LUN-1413: Update tests.py
Add exclude url names attribute.
LUN-1413: major admin refactoring
* fixed urls submission
* added next button in add form; renamed widget template
LUN-1413: fixed disallowed choices list.
* removed exclude_patterns from module definition
* pepified code; fixed add form; moved helpers import inside functions since it requires urlpatters to be already loaded;
LUN-1413: fixed tests
* prevent multiple form submissions.
Merge pull request #12 from pbs/LUN-1413

Lun 1413