Changes

Adjusted Shift code to support Phantom slots

Yes, this also was stolen from Railcraft. Its also much more robust than
the code BC was using.
 (commit: 0a18ae3)

Transactor Optimization

It was an O(n^2) operation to insert an item. Now its just O(n). The
functions for checking to see if a stack is valid in a slot are
expensive and should never be called more than once per slot, let alone
n^2 times (where n is the length of the inventory).

Additionally, by wrapping inventory in a slot iterator, I was able to
eliminate the need to handle FSided and VSided differently from
IInventory.
 (commit: e342084)