This is the last missing bit in automating POWGEN reduction for
container names.

The "empty" column should actually have been "vanadium_background" and
this adds better support for "empty_instrument" and "empty_environment".
Disambiguating the names should help people understand what is going on
better. Also adding support for the additional characterization files
will be used in the future development of PDF.

Another point when all of the tests work. The table has been expanded
to include two more columns.