Convert OAuthServer to Transactions + EditEngine

Summary: Ref T7303. This application is currently stone-age tech (no transactions, hard "delete" action). Bring it up to modern specs.

Test Plan:

• Created and edited an OAuth application.
• Viewed transaction record.
• Tried to create something with no name, invalid redirect URI, etc. Was gently rebuffed with detailed explanatory errors.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T7303

Differential Revision: https://secure.phabricator.com/D15609