Also cleanup a minor detail in stl plater

This reverts commit a2c0d7a4.

We used to have our own gcode analyzer in gviz but this was clearly
suboptimal and broken. Position of drawn things should not differ in
anyway from the original GCode anyway.

Use precmd() method instead of adding our own layer of preprocessing

This simple workaround should simply ignore initial layers with little
to no movements, and thus avoid M190/M109 to destroy ETA prediction.

basetrans was not updated before computing the real coordinates, thus
leading to invalid rectangles

This is needed to get sdlisting updated before checking it in the echo
condition.