G2S Rostock Mini base stabilizers

I redid the design from scratch. Improvements include:
* requires no drilling of new holes, attaches to motor mount screws (you will need longer screws to attach the motor mounts).
* slightly thicker for more stability
* more triangles to improve stiffness
* 3 tiewraps per rod instead of 2. Also go higher up the rods.

There is a calibration piece because my own printer is not very accurate in scale and it is important that the parts fits snugly to the rods. If you need to tweak scale print the calibration piece first until it fits.