Add support for querying feed transactions by author and date range

Summary: Depends on D20531. Ref T13294. Enable finding raw transactions in particular date ranges or with particular authors.

Test Plan: {F6463471}

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13294

Differential Revision: https://secure.phabricator.com/D20533