Allow entire buildables to restart/stop/resume

Summary: Ref T1049. Creates convenience actions at the Buildable level to stop, resume, or restart all builds.

Test Plan:

• Stopped all builds.
• Resumed all builds.
• Restarted all builds.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1049

Differential Revision: https://secure.phabricator.com/D7899