Override CARTOGRAPHER_THRESHOLD_SCAN to tell user if their printer is set to scan mode

[pellcorp]

Something like this should work, just needs some testing

[gcode_macro CARTOGRAPHER_THRESHOLD_SCAN]
rename_existing: _CARTOGRAPHER_THRESHOLD_SCAN
gcode:
    {% set mode = printer.configfile.settings["scanner"].mode|default('scan') %}
    {% if mode == 'touch' %}
      _CARTOGRAPHER_THRESHOLD_SCAN {rawparams}
    {% else %}
      RESPOND TYPE=error MSG='Cartographer is configured for scan, not touch!'
    {% endif %}

So then if someone has accidentally set cartographer to scan mode, will show a more informative error, hopefully we can get rid of this in a later release.

[pellcorp]

This might work as long as printer.configfile.settings["scanner"].mode|default('scan') takes into account a mode change in save config, need to check that.