Laying the groundwork for Niflib to be able to work on systems with different...

Laying the groundwork for Niflib to be able to work on systems with different endian types.  All Read/Write functions now take NifInfo structures which are based by const reference.  These are also passed into the NifStream functions so they will have access to the requested endian type of the NIF as well.  Also added endian detection and swapping functions.