Implement NiBillboardNode flags
In Morrowind the animations for triggering Spell Absorption (white star) and Reflect (pink/purple star) on actors pulsate and rotate.
In OpenMW 0.40 they appear to pulsate, but they do not rotate.
That's probably because of the NiBillboardNode's flags not being implemented.
According to nifskope:
00 = ALWAYS_FACE_CAMERA
01 = ROTATE_ABOUT_UP
10 = RIGID_FACE_CAMERA
11 = ALWAYS_FACE_CENTER
What we've currently implemented seems to behave like "RIGID_FACE_CAMERA" does in vanilla. The nodes in magic_reflect.nif and absorb.nif are set to "ALWAYS_FACE_CAMERA".