Change: Revised Monorail and Maglev Roof sprites

[supermop]

Tried to remake this PR with renamed branch

Edit 2TT to add info from #44:

The Open GFX Maglev station roofs do not quite match the Rail and Monorail roofs in terms of level of detail or pixel art style - generally they could just use a bit more love. I've tried to make the curved spaceframe portion more substantial by giving it some chord depth with a lower layer, and split the coloring to be silver on top and CC below. I've also added a CC stripe to the rather plain black columns. I added a bit more depth to the CC clerestory on the Monorail roof while I was at it.

[zephyris]

Changes look nice to me, particularly the chunkyness of the maglev roof (and I've been inspired by it, and made similar adjustments in OGFX2).

A quick update, for posterity, to describe the changes to the graphics in the PR description would be nice.

[2TallTyler]

There's discussion of the changes in #44. Also, commit checker is failing for incorrect commit title format.