heterodyne: Remove temporary file name no longer used.
heterodyne: Allow for poorly or undefined median in the overlap region.

Jan came across some data with entirely bad or mostly bad values in the
subband overlap regions leading to an undefined median.  Using a
default of zero will not be far off the mark.  If this is not done
the bad value offset is propgated along the sequence of subbands.
heterodyne: Add recipe parameters to control trimming of noisy spectral ends.

This is a continuation of 20a126ebd055a63e5.  There may be more to
come.
heterodyne: Correct errors in the prologue.
heterodyne: Add new primitive to correct baseline offset in line forests.

It currently has only been tested for hybrid data.
heterodyne: Invoke the baseline offset estimator primitive.