Gittrac #3930:  Initial partial implementation -- I'm not sure if
this is exactly how we want to do it (see remarks in ticket).  Also
no documentation yet.
Gittrac #3930:  Cleaned up code and test (of initial implementation
-- may need further cleanup after LIGO tries it).
Gittrac #3930:  Documented this.
Gittrac #3930:  Improvements to documentation.
Merge branch 'V8_1-gittrac_3930-branch'