videodb: add file_link table to possibly link multiple files to a single movie/episode/musicvideo
videodb: silence warning
CGUIWindowVideoBase: remove unused AddToDatabase() method
videodb: add GetFilesForItem()
videodb: extend AddMovie/AddEpisode/AddMusicVideo to add a new file for an existing item
videodb: simplify GetMatchingTvShow()
CGUIWindowVideoBase: remove unused override of OnClick()
videodb: don't add duplicate movie information
videodb: don't add duplicate episode information
videodb: don't add duplicate musicvideo information
CVideoThumbLoader: load streamdetails for all files of an item
CVideoInfoTag: add SetFileDetails() to assign all file-specific details