[mythtv] Automatic deletion

[Anduin Withers]

> If you want a program to never be deleted, then set it's rating
> very high (like 1000) so it would always have the highest rating
> and never be auto-deleted.

Everything except this bit was rather what I had in mind. While I haven't
used the rating system yet I don't fancy using it to artificially inflate a
program's deletion schedule. There should just be another flag so people can
preserve what they like. Maybe someday with more complex recording
"profiles" it could even be determined when setting up the recording type.

--
Anduin Withers