Adds a semi-coherent search class

- Also changes the parameter vector in the normal fully coherent search
  to remove the tstart and tend. This is done by wrappin the
  run_computefstatistic_single_point in a compute_fullycoherent_det_stat
  function
- Removes theta0 from the saved data dict for the MCMCSearch
- Adds example usage of the semi-coherent search