Migrate approval radio buttons to new REST API

PublishCommentScreen now uses two RPCs, one to the old gwtjsonrpc API
and one to the new REST API. The new style API lists verbatim the
valid approval categories and values on a per-user, per-change basis
rather than reading them from the sitewide config.

Change-Id: Iaada19112cfbe970dff26be570487b4d1ff3f6a2
8 files changed