added support to read the nif header separately. seems logical to see ahead what kind of file do we have

added support to read the nif header without reading the entire file. useful to check what kind of importer should be used to read the file.

niflib:  Update to latest xml.  Add helper properties.  Allow skinning routines to use BSDismemberSkinInstance instead of NiSkinInstance.

niflib:  Add InertiaMatrix as first class niflib type. Add qhull to niflib. Add UpdateMassCenterInertia to bhkRigidBody and supporing bhkShape objects.

niflib: Update to match nif.xml.  Replace Float4 with Vector4.  Use Vector4 in bhk objects.  Introduce default values for array types.

syncing niflib with xml (note: Union field missing from BoundingVolume; see niflib hack in docsys/nifxml.py)

Separated reference counting features of NiObject into new RefObject class.  This way they won't be buried in the obj folder.
Started adding NormalizeKeys functions to data objects, interpolators, and controllers that deal with keys.  Not yet finished.

Deleting RagDollDescriptor.cpp and RagDollDescriptor.h so that they can be replaced with versions that don't use a capital R.  Seems someone changed the case of this object in the XML file after it had already been included in Niflib.