Revised Schwibbogen

I improved on the small version of the Schwibbogen Smithy:
- cleaned up some unnecessary paths
- widened some parts that were too tiny
- added a base ala http://www.thingiverse.com/thing:17240
- removed some parts I didn't know where to put when assembling (may add them in a v2 when I can identify them ;))

I also changed everything to 3mm plywood and put it on a 400x300 sheet (the material available at my local FabLab).
Paths to cut have a width of 0.01mm, paths to engrave are 0.5mm.