Summary:
Ref T4324. The server code is probably going to get a fair amount more complicated, so allow it to load Javelin classes in a mostly-reasonable way.
This integration has a few warts, but should be good enough to let us manage complexity through the next iteration of the server.
(Mostly I just want the concicse Javelin mechanism for defining new classes.)
Version bump is just so I can figure stuff out if this creates any issues for users based on which version of things they're running.
Test Plan: Started server, posted some messages through it.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T4324
Differential Revision: https://secure.phabricator.com/D8253
