Change Z travel acceleration to decrease noise

change Z travel acceleration from 100 to 150 in eeprom and repetier make
Z movement less noisy
Add Clean Nozzle function

In quick settings add new clean nozzle function, it is also available
using M100 command
It do home if not done and ensure bed is at least 15 mm
it is supposed ok on DaVinci 1.0 and 2.0
Configuration.h has new parameter to enable and control mouvement
Avoid nozzile to hit metal plate when homing

Move Y in 7 to avoid nozzle hit metal plate after homing - Thanks Aaryn