More flexable tuner card support layer

[ggee]

Enhance the layer that handles the tuner card support to be more flexable to supporting new cards. I'm not sure how MediaPortal supports so many cards, but I believe it is mostly because of the way they can add support by putting a graph in a file. MediaPortal has the best tuner support I have seen, but gets a failing grade in the PVR features.

Greg

[sub]

To be quite honest, I'd rather just support the smaller set of cards already supported by GB-PVR. A wider set of cards will just lead to a wider set of problems to worry about.