[Help Wanted] Multi-character module support

[jhoff]

Should be able to allow a single module to drive up to 3 characters. Currently, each PCF8575 I/O expander is configured to only drive a single character ( P00-P003 for the motor and P17 for the hall-effect sensor ). It should be possible to simply run wires and power for up to 2 additional motors and sensors, connecting them to the unused pins on the expander.

Ideally, this should be documented / standardized in a way that we can make configuration simple. In other words, keep the current pin assignments as-is to allow original modules to work and then select specific pins for character 2 and specific pins for character 3, so that the pins can remain hard-coded in the firmware and only the module size needs to be configured via the UI. Should be able to add moduleSizes as a integer vector in the same way as addresses and offsets are configured now.