[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
videoplayer: adapt lateness detection and dropping to buffering
video player: present correct pts to user for a/v sync (after buffering in renderer)
videoplayer: some rework and documentation
renderer: bump buffers to 5
videoplayer: update frametime, it might change due to fps detection
videoplayer: give streams with invalid fps a chance for fps detection
dvdplayer: allow rewinding at end of stream, do a seek after rewind
dvdplayer: observe pts counter overflow
dvdplayer: avoid short screen flicker caused by unnecessary reconfigure of renderer
vdpau: advanced settings for auto deinterlacing