/rtp can now be used in the nether

There was a bug where if you happened to spawn at the very edge of a chunk or edge of a cliff, you slip off while the neighbor chunk loads. Made it so where you spawn at the center of the block opposed to the edge of the block.

Second attempt to fix spawning inside a wall. Issue was that i would teleport while the chunk was loading and if i went too far down before the chunk was finished loading, i would get trapped inside the wall.

Now the chunk loads before player is teleported and it checks to make sure the chunk is loaded before teleporting.

Please report if you still have issues with wall suffocation!

[x] Added Nether support (extremely OP - can find fortresses easily!)
[x] Cannot be used in The End, error is sent to player instead
[x] Fixed spawning inside wall

Removed teleport messages i was using for debugging.