Allow "Track Only" and "Autoclose" to accept regular expressions

Summary: Fixes T2564. See screenshot.

Test Plan:

• Made a bunch of valid and invalid adjustments here and verified that the branches table showed autoclose state and branches consistent with the settings.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T2564

Differential Revision: https://secure.phabricator.com/D10349