test: Add test programs

Signed-off-by: Jason S. McMullan <jason.mcmullan@netronome.com>
x-motor-encoder: Rename .ino file

Signed-off-by: Jason S. McMullan <jason.mcmullan@netronome.com>
powderbed: OpenSCAD updates

Signed-off-by: Jason S. McMullan <jason.mcmullan@netronome.com>