Make project membership edits use transactions and PHIDs and not be awful

Summary:

• Split project profile editing apart from project membership editing.
• Make project membership editing simpler and easier to use.
• Drop role / owner stuff from the UI.

Test Plan: Added and removed project members. Edited project profile information.

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D3184