Cleaned up interface between connection objects and endpoints.

Connection objects are passed into endpoint's initializer and then the
endpoint registers with the connection object.

Also began adding blocking for waiting until an endpoint runs its
onCreate method.  Importantly, for those connection objects for single
endpoints, the single endpoint must manufacture a false signal that
the other endpoint has finished its initialization.
Began adding code for oncreate initialization.  The checked in test hangs.  Should fix.