Fix issue with alternating shared save configurations from different worlds
Each BiomeDictionary Type is represented by an attribute. Custom attributes can be added similarly to custom biome groups.
Neither Attribute IDs, BiomeGroups, or BiomeMappings are not allowed to be the same. BiomeMappings overwrite Attribute IDs overwrite BiomeGroups.
Attributes can be added to BiomeGroups by adding their name prefixed with 'A|'
BiomeGroups should store their content strings used to determine applicable biomes and attributes
Attributes and Mappings can be added or subtracted when resolving biomegroups by adding a '+' or '-' in front of their names.
'+' is the default operator.
Add 'allbiomes' attribute.
Call BiomeDictionary registerall() to ensure all biomes are registered in post-init.
Remove old unused method to clear vanilla spawnlist
Merge branch 'feature/biomeAttribute' into dev0.9
Closes #51