* Properly handle G0/G1 with no X, Y, Z coordinates in relative mode
instead of duplicating coordinates - should fix #1675
* Only take move commands with X, Y, Z coordinates into account for
model size calculation - this makes our internal GCODE analysis behave
like the GCODE viewer's analysis and produce the same model size. The
downside is that extrusions on the origin are no longer taken into account
for checking if a model is within bounds of the print bed, but that should
hopefully not produce any issues in the real world.