U-Joint shortcuts

[Philippe Hurbain]

Since the center and end colors are always the same (except in one case), I think there should be 3 shortcuts:

One with ends and type 1 center all in color 16
One with ends and type 2 center all in color 16
One with ends in color 16 and type 1 center hard coded color 76

This is probably the best compromise between library complexity and ease of use. Actually I've been very happy with current single shortcut, as most of the time it needs inlining anyway to get proper angle, and then it's very easy to change color or middle part type. The only marginal benefit of more than one shortcut is to provide replacement shortcuts for boms (and your 3 shortcuts scheme works fine for that).