Re-creating just_leg_test

This is creating the just leg test stl again. This should not be pre-built in case how we build the legs of the microscope changes.

@kasbah can you update the ninja build script. I don't understand it? The command to run is:

openscad -o just_leg_test.stl -D big_stage=false just_leg_test.scad

Closes #160 (closed)