Update Television/Movie differentiation to match upstream.

This changes the definition of a television show to be anything where
the season or episode number is greater than zero. Television pilots are
often episode zero, while specials are season zero.
Pull new metadata from source even when existing metadata exists.

This forces the grabber to pull new data even when the inetref is
defined for a recording.  This is to work around an issue that the
mxml format has no proper support for local artwork.