The variable name was misleading and hence renamed

This renames the input sftfilepath to sftfilepattern and adds
documentation on how that should be used, i.e. a colon separated list of
wildstring or exact matches. In globbing for all matches, the colon
split is added in. sftfilepath is still used by `Writer` since
an exact path is known.

Note that the dynamic injection is currently broken - it appears to only
be injecting the signal in one set of data

This adds a class to perform follow ups from semi-coherent to
fully-coherent using an MCMC search.

- Also changes the logic of the MCMC search to check for old data only
  in the run method.
- The nsteps argument exists for the MCMCFOllowUP, but is unused.
- Some work on the plot_walkers to allow for overplotting. It may be
  useful to use this for the usual calls as well so that we don't have
  an initial and walkers plot?

- 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