heterodyne: Remove the FINDCLUMPS configuration file.
heterodyne: Factor out histogram peak finding to _FIND_HISTOGRAM_PEAK.

This was the location where the histogram-peak code was initially
developed.
heterodyne: Record that the subbands have been merged.
heterodyne: Cope with hybrid spectra that are already merged.

The extra code added in commits such as b8ec38866730 using the subfrms
method was unfamiliar because this technique is not widely used; the
merging of hybrid spectra comes early in the recipes, but I had added
the various filters in a too-advanced location before I had encountered
hybrid data.

It seems better to incorporate the full spectrum, lest only some
subbands are rejected within a spectrum.  Also the full spectrum gives
better definition of the emission.  However, leave in the subfrms code
to offer flexibility and to continue working with older versions of
recipes where the merging is performed after bad-spectrum filtering.
heterodyne: Cope better with wide wings in the histogram.

Introduce two options to prevent bin sizes that are too wide to obtain
a decent estimate of the histogram peak.

a) Use skewness and kurtosis to judge if there are extended wings,
and then evaluate the Freeman & Diaconis formula to set the bin width.

b) If the peak bin contains more than 15% of the sample size, decrease
the bin width with a fudge factor allowing for the drop off around the
peak.
heterodyne: Offset by one histogram bin.

I've long felt that the peak co-ordinate returned bty FINDCLUMPS is
displaced.  It appeared as a full pixel but a t first I could only
conceive of a half a pixel shift arising from the co-ordinate
associated with a bin being at the centre not the lower limit, but now
looking again at histograms where the peak bin is well defined plotted
in pixel co-ordinates, FINDCLUMPS position is consistently off by one
bin.
heterodyne: Remove diagnostic.

This retained the histogram NDF for debugging.
heterodyne: Typo and blank line removed.