Sort approvals in REST endpoints and approval table

Document REST endpoints to return approvals within a given list by
timestamp, although the timestamp is not exposed. Sort labels by
corresponding ApprovalCategory position.

On the client side, sort users by the owner first, followed by users
with nonzero votes.

Change-Id: I68cd21e4a62b76bd7de2bf1dd1e18e8675dd34db
6 files changed