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
Turned off Serial mocking, so the program needs and actual GRBL board to talk to.  Reverse this change for further arduino-less testing
Default Arduino port now chosen on MacOS.
Added TODO.txt
Added support in Gcode for changing feed rate without moving laser head .
Added basic (not yet working) engraving support & an example image
checkpoint commit— engraving still not working.
Changed default cutter dimensions to 360mm by 280mm.