[FluidNC PR#1430] Generic vfd small bug fixes

Bug fixes. Mostly minor changes:

– Division needs to occur after addition in ‘scale’. Otherwise you get truncation errors.
– GenericProtocol should grab the name from the spindle instance. This requires member functions.
– Added ‘ignore’. Since everything is 16 bits in modbus, that makes sense here too.
– There’s a bug in the initialization sequence when the configuration is incorrect. Currently not fixed; not sure what the best approach is.
– Fixed some insignificant little bugs in the Siemens, NowForever, etc.