Ensure default spawn isn't in middle of an ocean

[markkrueg]

Sometimes default spawn will end up in the middle of an ocean biome. It wasn't so bad when this happened with lakes; but this is a bit more of a "death trap" with larger oceans so should probably be tested for. Default spawns should probably always be not water

:-)

[msjyoo]

I fail to see how this is a bug. Does Vanila MCPE have a restriction on spawn locations like this one?

But this could also be implemented as a PocketMine.yml option

[dktapps]

This is certainly a death trap when the HELL generator is used (spawning in a lava lake is definitely not okay!)