TNT: Track TNT owner in metadata for protection mods

TNT: Track TNT owner in metadata for protection mods

It is useful for protection mods to know who owns an exploding
TNT block. This allows the blocks destroyed by the TNT to be
limited to the same ones the owner could destroy without using
TNT.

TNT placed within a protected area by the area owner, and later
ignited by another player will destroy within the protected area
nodes the igniter may not otherwise be able to interact with. Any
player could significantly increase the size of an explosion by
placing more TNT in an adjacent unprotected area if the original
TNT block was placed withing 1 node of such a boundary. This
feature sounds dangerous, but we are talking about TNT. Players
should use it carefully.