Feature and bugfixes [SEE DESC]

Added TNT and Hopper minecarts
Fixed piston code failing without an extension set
Repeaters are now broken
Fixed not being able to place a minecart on an activator rail
Added much needed comments on piston code
Fixed minor formatting issue
Merge remote-tracking branch 'upstream/master'
Compilation and Minecart fixes
Possible entity ID fix?
Another compile fix
Merge pull request #101 from tigerw/master

Fixes and features