New coordinate calculations for head penumbra filter

Corrects issues with coordinate system calculations for the head penumbra filter.    Head penumbra filter now works with multiple positional streams.   Filter initial cutoff frequency lowered to exaggerate the effect (will be tuned further over time).
-PI/2 is incident to the left ear
+PI/2 is incident to the right ear

Directly behind the head is -PI (= +PI)