Added META.{yml,json} files

Added META.{yml,json} files

- Added META.{yml,json} files similarly to fixing this bug filed against
  IPTables::Parse:
    https://rt.cpan.org/Ticket/Display.html?id=75366
- Minor bug fix to ensure not to look for 'extended' hash keys in returned
  IPTables::Parse data without an existence check first.
- Added the ability to specify 'ip6tables' when instantiating an
  IPTables::ChainMgr object via 'new'.
- Updated license to the Artistic license.