Added optional support for [vizlib] to visualize the grid. It's optional because it doesn't seem to be as useful as the standard entity based grid. The grid created by vizlib doesn't have the bug of disappearing depending on where the player stands but with all the movement it is hard to see the grid at all.
Formspec tweaked.
Some code hardening and updating depricated usages with backward compatibility as far as possible.
Added optional [xcompat] support to ensure craftability for all games supported by [xcompat].