Updated Limbo Decay Immunity

Updated the list of blocks that are immune to Limbo decay to include
Golden Doors and Golden Dimensional Doors.
Fixed Client Gateway Notification and NPE

Fixed the issue with clients not receiving notifications of gateways
being built into the world because we were modifying chunk data
directly. Our schematic classes now support building through World
instead of directly writing to the underlying chunks. Also fixed an NPE
that was introduced last night when I changed which line
GatewayGenerator was initialized on in mod_pocketDim.
Merge pull request #139 from SenseiKiwi/master

Various Fixes