Rolls back two-stage connection, putting complete connection info
into the connection files. This makes it easier to use hand-crafted
ssh tunnels, as all ports are read from the file, rather than
from the reply to registration/connection requests.
It is no longer possible to connect to the Controller without a connection file.
Adding the serialization methods to the connection file also makes it
harder for custom serialization to result in a mismatch in configuration
between the various objects.
cleans up EngineConnector and registration messages further, only storing single UUID for each engine (all the stored UUIDs happened to be the same already).
Message spec docs updated to reflect changes to message formats.