alpha:
-   support for more playlists
-   playlist: configurable columns

other TODO:
- don't quit by closing mainwindow?
- more advanced search in library
- queueing (MPD feature?)
- spectrum analyzer
- tagger
- split library by letters (like Amarok)
- icons could use a lot improving
- waste less memory (library and playlist are main suspects)
- Lyrics - should use only Qt's xml functions and allow user to select lyrics
- Get rid of the Settings widget. It's mostly useless -- its functionality
  should be moved to the plugins themselves
- switch to python3? -- waiting for PyQt4/PySide py3 support in Debian
- try PySide?
- support new MPD features:
    -- replaygain
    -- stickers
    -- mixramp
- review and cleanup everything
    -- MPD interaction layer -- rewritten completely, should be somewhat fine
    -- nephilim_app
    -- main window
    -- settings widget -- to remove
    -- connection widget
    -- plugins architecture
    -- the plugins themselves