Get Modbus/TCP PLC simulator and unit-tests working
o Ship modbus_sim.py and install /usr/local/bin/modbus_sim script
o Make sure we wait for the modbus_sim to start up for unit tests
Clean up remote.plc... unit tests
o Import with namespace, due to use of 'plc' name in tests hiding module
o Await stoppage of remote.poller to avoid logging when simulator exits