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 come from probe the firmware use the value present in Z_PROBE_OFFSET_FROM_EXTRUDER, but if the input come from endstop it use Z_ESTOP_OFFSET_FROM_EXTRUDER.
- Printing of Estimated Time to End just below of printing time, I’ve shorted 6 char the bar.
- In the Prepare menu I’ve add the 4 3DTouch command (Reset/Autotest/Pin down/Pin Up).
- In configuration.h I’ve put step_per_unit for T8, but you can found also the old line for M8.