Beginning to add things in entity.model. Also, refactored
util.Interpolation in such a way that allows for somewhat nicer client
code in that Interpolation.Type isn't required for dynamic interpolation
selection (although Interpolation itself arguably suffers in terms of
niceness).

Also, it's now possible to read from and write to uncompressed NBT
files.

Also, as with every commit recently, Container and such has been tweaked
in some way.

Also, miscellaneous javadoc.