0.5.1 Alpha Released

This release is largely an art update.

I've finally managed to get the plating blocks to work to my satisfaction, including slopes.  This update eliminates the sloped versions of the blocks and adds the slopes to the originals as an alternate shape.  This also restores the plating blocks to their original form, including edge pieces.  However, it still includes the more recent grunge  factor and shininess on certain blocks.  I hope it's the best of both worlds.

I must say, I'm particularly proud of the Titanium Hex Plating alternate shape.  It's not a sloped version, but instead removes some of the decorative trim, making it look half-finished.  I've always imagined this block as being assembled from a modular kit of pieces.