Change the way 2D filtering works to (by default) use one filter.

* Unless the user specifies otherwise, try to use one filter
 for both bands based on the band 1 FWHM, etc.  However, a
 mechanism for different filters in each band is provided.
* Lots of interface changes in command line routines to support this.
* Bump version number to 0.3.2.
Fix str len in analyze_pofd_coverage, correctly parse --sigc, --sigma_matched
in pofd_coverage_runSim

* User arguments --sigc, --sigma_matched being ignored in _runSim,
  which meant that sigma_matched was always the instrument noise
  and --sigc the default value.
* Truncate descriptive strings to desired length in analyze_coverage,
  add optional argument to set that truncation length.