Add SCARAcal to Smoothieware

Required for easy SCARA calibration, using M360 M361 and M364 calibration routines as
described in http://reprap.org/wiki/G-code

 Changes to be committed:
	modified:   src/main.cpp
	new file:   src/modules/tools/scaracal/SCARAcal.cpp
	new file:   src/modules/tools/scaracal/SCARAcal.h