Enlarged Rostock Idler End V1.2 for 12mm Smooth Rod

Rostock Motor End originally from Jcrocholl

- V1
- Thanks to the excellent parametric setup
no change ere necessary for this file the change
made to bracket.scad where directely useable
- V1.1
- Added stiffeners to better carry the load of the pulley
I hesitated with the boxed concept but I guess this will keep
the pulley accessible
The switch holder is not usefull anymore
- V1.2
- E