Implement PhabricatorApplicationTransactionInterface on PhabricatorUser

Summary: Right now, "Publish" workers for user profile edits (title / blub) can get gummed up in the daemons. Implement the interfaces and provide a Query so they can go through.

Test Plan:

• Made a profile "Title" edit.
• Used bin/worker execute --id <id> to see task fail.
• Applied patch.
• Saw task work.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D13213