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).
I want it in a log that is switchable (at runtime) and both by "debug level" and by the "subsystem".  We don't quite have that yet, and it was suggested (by Brad) that we use qDebug here.