Use non-strict version of getBiomeId for LayerBiomeBorder
Add Bukkit logs to .gitignore

These were created by the unit tests.
Fix biome name being overwritten by non-virtual biome name

Fixes #276
Build script: update Shadow plugin to 1.0.1

It now seems to work correctly with ForgeGradle, so our little hack is
no longer needed.
Rework mob spawning to better interact with biome inheritance

Fixes #275

If you created a biome DesertMod extending Desert, it would have
SpawnCreaturesAddDefaults: true and SpawnCreatures: []. This would
result in cows/pigs/etc. spawning in the DesertMod biome, as those are
the default animals of custom biomes.

This behaviour is not intuitive, so it has been changed.
Spawn*AddDefaults is now gone, you need to specify the entity list
yourself. The biomes have correct default settings.

Care has been taken to ensure backwards compatibility. Old configs with
Spawn*AddDefaults present automatically have the default mobs added.