Fix wiki links.
Merge remote-tracking branch 'rapns/master'
Improve compatibility with official active record API.

- change_column_null isn't officially supported (espacially in the jdbc h2 implementation)
- see http://api.rubyonrails.org/classes/ActiveRecord/Migration.html
Add support for testing the jdbch2 adapter.
Fix (NameError) uninitialized constant SQLite3::Exception
Merge remote-tracking branch 'origin/h2_support' into app_sync

Conflicts:
	config/database.yml