[pvr] remember last watched group
[pvr] set the last played group as selected group at startup
[pvr] rewrite of SearchAndSetChannelIcons() to use directory listing
[pvr] adds a background job to search for missing channel icons

This adds a background job to search for missing channel icons, which is exectued on every PVR manager start.
[fixed] Fullscreen lost on alt-tab with non-masterprofile
Merge pull request #4657 from xhaggi/channel-icon-scan

[pvr] rewrite of implementation for search of missing channel icons
AESinkPULSE: Start stream corked. Resume when starting to add packets
Merge pull request #3988 from xhaggi/remember-last-watched-group

[pvr] remember last watched group
Merge pull request #4670 from fritsch/pacork

AESinkPULSE: Start stream corked. Resume when starting to add packets
Merge pull request #4667 from a11599/fixfullscreenloss

[fixed] Fullscreen lost on alt-tab with non-masterprofile