niflib: Update to latest nif.xml

include/gen/RotationKeyArray.h

include/obj/NiBillboardNode.h

include/obj/NiSourceTexture.h

src/gen/Header.cpp

src/gen/MultiTextureElement.cpp

src/obj/BSShaderProperty.cpp

src/obj/NiGeometryData.cpp

src/obj/NiParticlesData.cpp

src/obj/NiSourceTexture.cpp

src/obj/NiStencilProperty.cpp

src/obj/NiTextureEffect.cpp

src/obj/NiTexturingProperty.cpp

src/obj/NiZBufferProperty.cpp

src/obj/bhkNiTriStripsShape.cpp

src/obj/bhkPackedNiTriStripsShape.cpp

src/obj/bhkRigidBody.cpp

src/obj/bhkWorldObject.cpp