West-East and North-South corridors can now have hell deaths

*There are now 3 supported spawn point scenarios:
1) The original south spawn points scenario requiring plenty of south
space.
2) A south spawn point scenario which can occur in 1 tile width
north-south corridors.
3) A east spawn point scenario which can occur in 1 tile width west-east
corridors

* The grim reaper can now use the lava hole's west use tile.

*World:getHellDeathSpawnPoints() -> World:checkHellDeathSpawnPoints()

* World:checkHellDeathSpawnPoints() is now simpler with no duplicated
code.

+World:lavaHoleUseTileUsable()