Replaces the hard-coded biome list with an automatically generated list of available biomes, except "custom".
Fixes a bug with setting the biome with a range, where if the range fell outside the region it would expand the range to include either the min or max region corner. This bug meant that if you stood next to the edge of your island and ran, for example, "/is biome 5", it could actually set the biome along the entire edge of your island (much larger than the specified range).
Adds a buffer when setting the entire island biome, if there's space for it. Just adds half the distance between island protection ranges. This ensures that, when possible, if a players sets the biome for their entire island it also covers the edges. Mojang changed biome resolution from 1x1 to 4x4 and added noise to biome edges, so previously if you used "/is setbiome ", it would miss a lot of spots along the edge of an island.