gstlal_feature_extractor: add dot graph for documentation, added separate groups for command line options, move imports around for aesthetics, change comment blocks (e.g. main) for documentation

Revert 9ac1b181

See merge request lscsoft/gstlal!1

This reverts commit 9ac1b181

gstlal_feature_extractor: propagated new waveform generation changes throughout, fixed some bugs/typos from switch causing pipeline to crash

- thinca() can now handle the cases where a ranking statistic has not been
  supplied but fapfar and/or min_log_L have been set.

- not currently used, but this plumbing will be needed to add source population models to the ranking statistic

- disable ln L assignment online until ranking statistic is sufficiently-well measured.  this is just a first hack to be better than nothing for the KAGRA testing being done.  it will surely be replaced by something else, later.

gstlal_feature_extractor: fixed bug in determining trigger time from buffer rows, now based on filter duration

idq_utils.py: changed implementation for generating sampled points for sine-gaussian and half-sine-gaussian waveforms

gstlal_feature_extractor_template_overlap + idq_utils.py: fixed bug in template generation causing missing templates, changed way templates are produced as a result, propagated changes to template validation code

gstlal_feature_extractor_template_overlap: added template bank overlap plot, aesthetic changes to html report

gstlal_feature_extractor_template_overlap: tweaked some plot params, added sampling of waveforms to plot to limit the number of waveforms plotted