Added JSON logging to iDQ vetosrc helper class. Also fixed un-necessary latency when there are iDQ files before and after a gap.

- for ER6 pre-release.

- burst code now moved to gstlal-burst

- add --samples-file and --samples-cache options, load counts from those
  files, and add them to the new counts we generate

- use OpenMP to auto-parallelize.  won't work on systems that don't use GCC
  or clang

- writing speed was always very high, but this enormously increases
  the speed with which the file's contents are loaded.  HDF5 doesn't
  seem to scale to large numbers of things in groups.

- replace log(1 + x) with log(x) for large x