Summary:
For T262, we need to query for revisions by affected path.
We currently have a class called "DifferentialRevisionListData" but it's sort of
nasty and it would have been really cumbersome to add this query to it.
Instead, this provides a query object more in line with ManiphestTaskQuery,
which I'm pretty happy with. I'd eventually like to get rid of
DifferentialRevisionListData but it's used in a couple of places right now.
Test Plan: Used phpsh to execute queries, got back apparently-sensible result
sets.
Reviewers: jungejason, nh, tuomaspelkonen, aran
Reviewed By: jungejason
CC: aran, jungejason, epriestley
Differential Revision: 978
