Allow repository push logs to be filtered by pusher and repository

Summary: Ref T4195. Add UI options to filter push logs by pusher and repository. Add a link from the repository view page to the push logs.

Test Plan: Viewed a hosted repository, clicked logs link, saw logs. Filtered lgos by repo/pusher.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4195

Differential Revision: https://secure.phabricator.com/D7713
Record new commits in the push log

Summary:
Ref T4195. Like the previous diffs, these both create a useful log and give us an object to hand off to Herald.

Surface this information in Diffusion, too, and clean things up a little bit.

Test Plan: {F87565}

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4195

Differential Revision: https://secure.phabricator.com/D7718