Calibrate Z-offset via LCD Menu. Initial commit. Not tested.
Choose "Calibrate z-offset" from prepare menu. The head will move home and the printer will start auto bed leveling. Then the head will be move to the center of the platform and lower down to z=0. Now the head is ready for calibration. With encoder it is possible to set z-offset and the head will move up or down accordinly. So find the position when nozzle is 0.1-0.2mm above the platform (the sheet of paper can pass between nozzle and the bed). Push the encoder and new z_offset will be stored in EEPROM. It will be applied after next HOME-AXIS command.
Fixed z-offset string macro
Fixed travel speed and submenu item
Rewrite calibration script with state-machine
Fixed timeout during waiting for head to move to initial position
Fixed minor bugs with moving head to initial position for calibration
Fixed problem with enqueuecomand buffer size
Fixed bugs with calibration state-machine after testing on Ultimaker
Removed commented code
Merge remote-tracking branch 'bevaz/LCD_Calibrate' into Marlin_Mendel_Config