tinytim ultimaker feeder

Decided to derive a feeder upgrade for my ultimaker over the weekend using only stuff I already had lying around.

This is a basic derivative of the stock ultimaker feeder, but allowing a rollerblade bearing to be used to press the fibre against the hobbed bolt using a spring-loaded end block.

The vertices in the model were placed by hand (approximately) but the whole thing prints fine and seems to work all right (so far).