Added $384 setting for controlling G92 offset persistence.
Improved $help command output and handling.
Moved the optional tool table in non-volatile storage.
Added gcode parameter support and optional expression support.
Added `$ESG` and `$ESH` system commands for outputting current setting definitions.
Added setting descriptions to most settings. Work in progress.
Added/updated preprocessor code for leaner board map files++
added some crossbar pin definitions and limited $TPW retract to Z home.
Moved some common driver code to the core and update of current position on steps/mm changes.
