R1:cc865e549bcd

Provide revision parent/child edges in `edge.search`, and more information in `differential.revision.search`

Summary: See PHI195. This bulks out these API methods since all the requests are pretty straightforward.

Test Plan: Ran `edge.search` and `differential.revision.search`.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D18762