[rbp/omxplayer] Reset display region when video stream properties change

Currently when video stream properties change, e.g. when user switches to next or previous Live TV channel, and has the same frame width and height, the COMXVideo::SetVideoRect() method is not called, causing the video to play back with default source and destination rectangles, not respecting the user-defined zoom settings.

This commit fixes the issue.
[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()
[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