[settings] pass the current video settings to SaveFileState job
[cosmetics] always create the save file state job on the heap
[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

This extends EraseVideoSettings to take an optional "path" parameter
which can be used to remove settings only for e.g. PVR channels and
recordings
[pvr] remove channel settings related functionality from the PVR parts since
they're now obsolete
Merge pull request #4783 from Jalle19/unify-channel-settings

[pvr] unify channel settings with other video items