#1 Endian issues in model class

[Ben Hines]

Compiled Possible Worlds on Mac OS X. It compiles and runs, but quickly crashes due to endian probelms in the model class. Fixing this would let the app work on LinuxPPC and other big endian systems as well.

model::read_int
model::read_sizet
model::read_float

all need to be fixed to support big endian systems. (it appears the data files are little endian)

There may be other problems, i didn't get much farther..