[settings] use SaveFileState() instead of SaveCurrentFileSettings()
[settings] don't ignore PVR channels in SaveFileState()
[application] create LoadVideoSettings() method
[pvr] remove most calls to saving/loading channel settings
[pvr] handle channel settings save/load when switching channels
[pvr] move functionality for deleting channel settings to VideoDatabase
[pvr] remove channel settings related functionality from the PVR parts since
they're now obsolete