So far the plugin selected the gcode script corresponding to the number of
extruders configured in the printer profile. After a close look into the
implementation in Cura itself, prompted by #1708, it turns out that this is
in fact wrong.
Cura selects the gcode script to use based on the maximum of the number of
extruders needed for printing the models in the scene and the minimum number
of extruders needed for generating support (if support extruder is "both" or "first"
or there is only one extruder, that's 1, if it's "second" and there is more than one
extruder, it's 2).
This commit changes the plugin's implementation to mirror this implementation.
The difference to Cura is that we have the number of extruders needed for the
models in the scene hard coded to 1 since we only support STL right now which
can never contain more than one object. If we ever decide to support merging of
multiple STLs into one single multi-extruder print or other model files like AMF
or OBJ from OctoPrint's slicer support, we need to change this.
20cd13904d