Hotfix/simplify app ownership

@polastre this should fix the test failures currently on devel ... though at the cost of some functionality ... 

- Remove whitelist for owners ... revert back to single owner
- Remove Memberships and many-to-many w/through (user will not have a relation to application for apps it is a 'developer' on)
- Keep developer_emails whitelist (this becomes a simple whitelist with no fancy mapping functionality)