NiPhysX block decoding

The blocks were almost entirely undecoded before, with incomplete linkage (Ref fields).  They are now completely decoded and I do not believe there were any regressions for past NIF versions, but it would be hard to test as I do not have NIFs before 30.1 with these blocks.

However the version conditions were all maintained and corrected on the fields that were already decoded for 20.x.