- don't construct ThincaCoincParamsDistributions instances just to hold
  temporary binned array data.  saves memory, makes it easier to move these
  methods into ThincaCoincParamsDistributions later if we wish

move binnings, filters and coinc_params funcs into CoincParamsDistributions

reduces thread count by about 10% and virtual memory foot print by about
the same (= ~1.5 to 2.2 GB in my test cases)

moves some arithmetic out of the outer-most loop.

- this patch hollows out all base_init() methods, moving their contents to
the class_init() methods.  gstreamer 1.0's boilerplate macros no longer
refer to base_init() so this could be considered 1.0-readiness work, but it's
also just tidier.

bin/gstlal_inspiral_pipe: update compute_far options to match new name, accept 512s segments instead of 256, which was too short