B-struder Bondtech edition

Update 1/30/2020:
- stronger Bondtech arm
- stronger spring cap
- lock lever tuning
- regen stls

So after using the Hobb-goblin version for a while, I wanted to have bit more grip and torque for multi-material printing with single-nozzle/multi-extruder setup. The filament changes can be demanding on the extruder.

Bondtech gears seem to be the optimal choice for grip so I went and modded the B-struder Hobb-goblin edition:
- Bondtech gear version of the arm obviously
- rotated the filament path a bit. Now the path is bit more in line with the rotation angle of the arm, reducing the skew. Not a big problem originally, but here it is all the same.
- motor mount plates are now 4mm thick
- couple different motor mounts that have different frame mount options
- added some small paths inside the motor mounts, which will cause extra perimeters to be printed -> stronger parts
- removed need for the 623zz bearings at hinge. The arm has holes that the motor mount and MR105zz suppor