Refs #1355, Refs #1356 - Fix problem with DVR dup detect.

Refs #1355, Refs #1356 - Fix problem with DVR dup detect.

I have completely removed global duplicate detection at this stage until
such time as I can do things properly. This means a user can ALWAYS manually
override and force a recording of a show.

For now duplicate detection only exists within the context or a series
link. So it will only record the "first?" instance of a given episode in
a give series link.

This is still a bit of a hack until I provide the user with the ability
to control the configuration and implement all the hooks properly.