Minecarts and undead-burning

Beauty and a beast.

Please see commit descriptions.

~~Could @madmaxoft make carthurts? I don't know how, and the carts are everywhere due to invincibility and testing :(~~ Partly done.

Oh yeah, there is also something seriously wrong with g_BlockIsSolid and some others. I had to change the solidity of rails to true for the physics handling to class it as non-solid. This may also be a cause of #127.