ERCF on RRF

WIP set of configuration and macros to enable running the ERCF on RRF

Usage

Add M98 P"ercf/lib/init.g" to the bottom of config.g

Edit ercf/settings.g to configure the drive assignments (M584). Stepper motor configuration, M569, can be done in config.g or ercf/settings.g

In order to run these macros, RRF 3.4b4 or newer must be used

Configuration

Many variables can be configured in ercf/settings.g, reference ercf/lib/globals.g to see what can be altered.