Add transaction-oriented editing to projects

Summary:

• Make some editing operations transaction-oriented, like Maniphest. (This

seems to be a good model, particularly for extensibility.) I'll move the rest of
the editing operations to transactions in future diffs.

• Make transaction-oriented operations publish feed stories.

Test Plan:

• Created a new project.
• Edited an existing project.
• Created a new project via quick create flow from Maniphest.
• Verified feed stories publish correctly.

Reviewers: btrahan, jungejason

Reviewed By: btrahan

CC: aran, epriestley

Maniphest Tasks: T681

Differential Revision: https://secure.phabricator.com/D1477