Minecart collision and general improvements

+ Implemented collision on one type of rail
* Improved curved rails somewhat
* Fixed a crash bug
Merge remote-tracking branch 'origin/master' into minecartimprovements
Added more rail functionality
Fixed weird meta with curved rails
Minecart improvements and fixes

* Fixed curved rails
* Fixed detector rails in certain situations
* Fixed powered rails and others passing bad meta to SnapToRail()
Added one more direction into collision checks

* Added direction XM_XP
* Improved performance, thanks STR and xoft
Begin implementing ascending rails
Added more minecart powered rail directions
Improved AllToLua UI experience
Rail speed tweak
Reduced unnecessary echoes (thanks xoft)
Merge pull request #589 from mc-server/minecartimprovements

Minecart improvements