Lane Bandpass Filter Oscillator

This is a bandpass filter oscillator that has an additional tuning parameter
in addition to the Period used by John Ehlers. It is 'quality' which has meaning
in a frequency/magnitude sense (See Q in line 7). The bandpass is slower
according to the inverse of Q.

The concept was developed by John Lane etal in the text 'DSP Filters'
The bandpass filter works better in a trending environment.