kf export: * bone animation priorities re-exported from NULL    constraints * interpolator without data gets its values restored
kf export:
* bone animation priorities re-exported from NULL 
  constraints
* interpolator without data gets its values restored

nightstrike/blender_nif_plugin,amorilia/blender_nif_plugin,nightstrike/blender_nif_plugin,amorilia/blender_nif_plugin