playlist: make kept song count collision resistant
actions: apply filter: apply initial filter if non empty
lyrics fetcher: update lyricwiki fetcher
lyrics fetcher: update sing365 fetcher
lyrics fetcher: update lyricsmania fetcher
lyrics fetcher: update justsomelyrics fetcher
lyrics fetcher: metrolyrics: remove code not needed anymore
song: initialize m_hash in default constructor
media library: add data fetch delay after position changes
playlist editor: add data fetch delay after position changes