this enables to do multi-detector trigger generator & coincidence analysis
by inputs of channel-name, data, template, and PSDs from multiple IFOs.
In short, this is lalapps_StringSearch + ligolw_add + lalapps_burca of old pipeline.

like the old burca

__lt__() and friends

- use `Requires.private` in pkgconfig files to stop forcing downstream
  packages to link against everything upstream
- added `pkgconfig` as `BuildRequires` for RPMs
- bumped required version of pkg-config to 0.18.0

Makefile.gstlal_feature_extractor_offline: fix issue with generating segments from int8s conversion, add default safety info, clean up comments and unused variables

gstlal_feature_extractor_pipe: link feature combiner job to run after all feature extraction jobs are finished

gstlal_feature_extractor_pipe: fix some issues with changed imports, update params in offline makefile

binjfind needs them to identify sim_burst <-> sngl_burst coincs

Makefile.gstlal_feature_extractor_online: update kafka server params, ability to run off of /dev/shm easily

feature extraction: change trigger_time -> time, remove nan rows, specify true spans of datasets to comply with gwtrigfind

Set_caps seems to be executed *after* start, so in the previous commit audio_info will not be updated before the safety check and stumbles there. After this fix things seem to be going, and a sane value for chisq is obtained.

- move files into a gstlal/ directory so that header files can be
  #include'ed using paths that will work inside and outside the source tree

in working state

update Makefile.gstlal_feature_extractor_online to produce a separate kafka dag targetted at dedicated nodesw

gstlal_ll_feature_extractor_pipe: remove kafka/zookeeper jobs, update feature extraction options to take in psd-fft-length

- port XML trigger table reading function to ezligolw

- move functions that are only used by gstlal_burst_triggergen.c into that plugin as static functions.

- upgrade to newer autotools script