Geeetech A10M Marlin 1.1.9 Firmware

This is Marlin 1.1.9 Firmware for Geeetech A10M printers with mixing extruder. I ported all Geeetech features from Geeetech's 1.1.8 version, which include:
- Full BLTouch support with my hack allowing to fine tune small build plate tilts which could not be eliminated by autolevel alone; BLTouch is enabled by default, disable it by commenting "#define BLTOUCH" line in the Configuration.h file if needed.
- Power loss recovery/resume. I tried to activate a native Marlin power loss feature but it