dawn: update for azimuth-rpc, wip
dawn: update for azimuth-rpc, wip

Contains the bulk of the changes, but is missing escape parsing,
doesn't handle missing optional fields nicely, and is mostly untested.

ngzax/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,urbit/urbit,urbit/urbit,urbit/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,ngzax/urbit