GEEETech i3B: Firmware

After the installation of my new GT2560+ and the 3DTouch I’ve restart use the original GEEETech firmware for mi Pro i3B…
…it work fine but I’ve integrate in this firmware some enhancement that I’d like:

- A dedicated pin for the 3Touch, in order to leave original endstop on Z Min as emergency stop in case of error with 3DTouch (now the firmware look in same time Z Min and Z Probe pin during Z Home)
- A define to manage the offset not only for Z_PROBE but also for Z_ENDSTOP, now if the input