Customizable Universal Filament Filter

Rework of the excellent original from [Creative Tools](http://www.thingiverse.com/CreativeTools) of their [Universal Filament Filter](http://www.thingiverse.com/thing:492067).
Originally in FreeCAD, now in OpenSCAD with the filament keeper at 45 degrees.
This helps to accommodate 3mm filaments better.

You will need to fiddle with the filament diameter and "Slot factor" so the filament can be pushed through the slot into its captive hole.

The Round base prints as well with no supp