Improve UPNP sort order for TV recordings

It can be very hard to use the current sort order for the content items over UPNP especially if you have large numbers of a title and don't know the exact date of the recording.

This patch adds logical folders for date sorted versions of the listings by title and it also applies a subtitle sort to the non-date sorted title list to help where you know the particular episode that you want.

I have tested these changes on Ubuntu Precise but have not built from the Git source.  I think that this is a very low risk change.

I understand if the design choices you make do not want to offer all these choices but as a heavy UPNP user I would strongly request that you do make a user obvious sort apply to the title grouped content (and I suggest by date).  I also understand if you need to change the names, especially if internationalisation is required but I wanted to offer this upstream anyway.