bhkRagdollTemplate support

Added support for `bhkRagdollTemplate` block based on two .rdt files (.rdt file is a .nif file) located in Fallout3 directory "meshes/ragdollconstraint". It seems that game uses only "Default.rdt" file. Second file "stiff.rdt" is unused and suspicious because in NiHeader it has User Version 2 set to 16 instead of 34 as all Fallout3 files (and also Default.rdt) have. Maybe this file is leftover. Adding support for this file complicated code for Fallout3 in compounds `RagdollDescriptor` and `LimitedHingeDescriptor` by additional version conditioning.
Can anybody check Fallout New Vegas files if there are present any .rdt files? It would be good to have more than 2 files for decoding. Or exists other games with these files?
@neomonkeus @skyfox69 @jonwd7 @Ghostwalker71 @throttlekitty @nexustheru @amorilia