Added Rotary Pot Comm-09939

Autodesk Inventor and STEP files. This part is physically identical to
rotary potentiometers COMM-09940 and COMM-09941.
Deletion of lockfile.lck
Added STL file for Rotary Pot COM-09939
Merge pull request #21 from Tomdf/master

Added Rotary Pot Comm-09939