Open-Inverter CAN control - incompatible with GearShift class

[Mitchy6]

Current Open-Inverter CAN control mirror the Digi-IO signals and output direct for the external OI control.
This is incompatible with the current shifter class, whereby Gear Shifters output Drive/Neutral/Reverse (D/N/R) status.
With the increase in supported shifters, it's more likely that someone will use a shifter with OI-Inverter CAN control.

Possible solutions are to:

• Incorporate D/N/R status direct into OI-CAN logic
• OR signals to add D/N/R to CANIO within Utils.cpp
• Map D/N/R via CAN output back into itself as CANIO

Quick/Dirty solution currently is that I've added D/N/R status to CANIO portion as an additional OR signal,
However this isn't a elegant solution. and the OI-CAN logic is the only inverter to use the Digi-IO signals direct.

Best solution is to Modify OI-CAN logic for D/N/R, and let the logic in Utils.cpp convert from Digi-IO to D/N/R, thereby unifying the Inverters to all use D/N/R

PR to follow after some initial bench testing.