HSSRHR: Halogen spotlight system rail holder replacement

Nothing special, just a replacement part... but the first useful thing I printed with my Printrbot LC :-)

This replaces the plastic holders seen on one of the pictures.

Fixed with Netfabb's cloud service as my model in Sketchup was a bit sloppy. The more recent version "4e" was just fixed in netfabb studio basic and still has some issues, but prints fine (on the printrbot/slic3r0.9.7).