Save jog step size

Save the user-selected step size
add various files to .gitignore

Add these to .gitignore:
	GrblController
	*.o
	moc_*.cpp
	qrc_*.cpp
	*.stash
	GrblController-local.iss
Start of visualization of grbl status

- Little widgets that highlight the grbl status (abs/rel mode, mm/in
units)
- Will extend later to more items
- Fixes to previous cockup with the jog in -ve direction
Add spindle state icon

- add icon showing spindle state
- add tooltips for the state icons
- hunting for the slow sending of commands (esp. when jogging), added
and tweaked some diagnostic output
- refactored the grbl state parser and simplified the incorrect
measurements logic
- cosmetic formatting fixes
- reduced some sleep times, seems to help jog performance
- added coolant icon