QU-BD One-Up Y-axis spacers & clamp

Replaces the original Y-drive spacers and the (not received) belt clamp.

The main spacer is a revision from thing [212982](http://www.thingiverse.com/thing:212989), i'm too lazy to measure the thread pitch.
Also reduces the thickness, the original one was to thick so the belt was passing over one clamp hole.

Updated 23/02/2014: made plates thinner to fit the printing plate.
Updated 15/04/2014: got this changes since Feb... made shim and plate thinner to fit print plate