Added non-working threaded code for sending Gcode files to GRBL.  Nothing’s hooked up yet, just better to have it checked in than not.
Checkpoint checkin.  More threaded behavior added, but not hooked up yet.
Load/run/ buttons hooked up and working, but thread seems to be blocking main thread.
Also added DXF-loading behavior, although that’s in separate code outside of this repo for now.
Merge branch 'master' into feature/rc_threaded_gcode_send_20140221

Conflicts:
	risha_controller.py
	risha_window.py
Added dummy_serial.py, as found at http://minimalmodbus.sourceforge.net/
Added flushInput(), inWaiting() and readline() methods to dummy_serial to make it work with RishaController
Serial mocking support for running without a live GRBL arduino
Refining UI behavior when submitting gcode via a separate thread.  Blocking issues remain.
Added manual arduino connection/disconnection UI