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