Mediaplugin deep integration

Please note that the following is no more than some thoughts on how OpenLP could behave. There are no plans yet to make this happen and there is huge possibility it never will be done. If this makes you feel uncomfortable, you need to get your hands dirty (current developers, you already do superb job, don't feel obliged).

Media by usage
All media could be separated into two:
 * standalone media like presentations, images, movies, trailers and other video, audio
 * background images and videos
 * themes would have no backgrounds data

Applies to both tabs

 * Tabs would need separation by media type, so the line below search bar has toggle buttons:
 * all, presentations, images, audio, video for standalone media
 * all, images, video for background
 * Named folders, which could be sets, you could drag folder to service or send it live, set could contain different type of media
 * Media tagging
 * Search by title, tags, filename
 * Open dialog would show all supported media (Supported media, Presentations, Images, Audio, Video, All files)
 * Drag and drop files into the area

Backgrounds tab
Selecting a background would last even after the theme change. Since songs can have backgrounds (along with themes), backgrounds tab would need a lock icon which overrides local background changes.
 * List contains thumbnails with additional data on right
 * Background media could be assigned to service items
 * Background folders behave like sets as well, picking random or next background every time when (optionally):
 * slide changes
 * a number of seconds is passed
 * video reaches its end

Media tab
Multiple files opened/dragged at once, text file with list of file paths, m3u and other playlist files would be imported into one folder creating a set
 * Possible extra data: time-stamp when imported, last time live
 * Video could be separated into chapters creating a subset (technically not possible yet, since we set a end for video)