Top mounted reel holder

This design has been superceded by http://www.thingiverse.com/thing:1835048

A remix from an own remix - why that?
* This is rather a quick hack, with mediocre code quality, rather than a "remix", consider it an early access version.
* The usefulness of this item is limited, as it is used in conjunction with http://www.thingiverse.com/thing:1792366 - as it's sort of specialised, I didn't want to modify the template.

I slapped on rod mounting brackets, added basements to the holder, and added the rod clamps, and pins to tentatively hold the parts together.

Purpose of this thing: rest the filament spool holder on the two rods which join the Z top brackets, above the print head, where it is positioned such that filement is fed straight into extruder, no force or lots of pulling required.
These holders won't fit on a printer without those horizontal rods.
Two parts sets are needed for one holder.

To improve: square footprint studs for rod clamps, print studs laid out horizo