Remove south migrations
Drop non-1.7 from tox
Move type, area, and base_template default to form initials.
Fixes to content type toggling and page admin

- Fix a bug in toggling pagelet content types, which wasn't used in the
  previous test bed for 1.7 support
- Fix URLs in README to include newly required selectable URLs for
  tagging
- Fix settings for content types
- Fix widget for content type in form