check for max bones per partition for 20.2.0.7-12-83 nif ref issue #130.

Fix for empty ninode bsxflag error

Rebreaking fliptext function until we can sort out exactly what it

should be doing

Refactor/texture import

dependency.

none not false.
used hasattr instead of try for setting tau and damping.

Minor edit to makezip bat to work with latest version of buildenv.

Feature/shader texture

current API

niftools.object menu

settings. Unified import and export error classes to nif_utils.NifError
for sanity sake. 

current nif files

user readable string.

renamed a few variables 

export

variables to import code.

being inside compressed library.

Collision matrix IO