-to later allow for CUDA implementation
 -some optional-import acrobatics
  to fail gracefully if a module (especially CUDA)
  is not available
 -as of this commit, nothing beyond lal implemented yet

 -first search should be standard non-transient GridSearch for comparison

Previously, this functionality was part of GridSearch, this splits this
into a separate subclass to ease future development.

 -new output: full (t0,tau) Fstat map,
  if bands in those params are searched
 -one file per Doppler grid point