AstronClientRepository

Implements ACR and fixes a few bugs.
This file seems to be a duplicate of MsgTypes.py, which we've modified to include the Astron message types (removing/deprecating the Disney-OTP ones).

If we want to preserve OTP support and add Astron alongside it, that's fine. I'll have to talk to @rdb about whether or not it's worthwhile, however, considering OTP is now a dead project.