Add a normal "view" page for Herald rules

Summary:
Ref T2769. This will house the transaction list and replace the "edit log" stuff.

The UI is a little bit rough and can probably share more code with the transaction history, but seems mostly-reasonable.

Test Plan: {F53253}

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2769

Differential Revision: https://secure.phabricator.com/D6690