Start migrating to mutl-project friendly API

This PR updates the API which Activator uses (the high level API) to support multiple projects.  It also consolidates the protocol into one file with a better delination of what is high level and what is low level.   

We may need more requests here to fully support both IDEs and Activator at a high level, but this is a good start

It also brings in the start of the low-level API for sbt inspection type commands.

The rest of the code is slightly gunky (more cleanups possible) but working.  This represents the next release in the series of sbt-remote-control (a 0.3).