0.5.4 release
    
    * Dark style support added (Github issue #134)
    * Bugfix: Removal of debugging noise (Github issue #139)
    * Bugfix: Allow removal of user-defined levels with names of a built-in level
    * Bugfix: Make sure that all user-defined levels are displayed in "Specific domain level configuration"
      settings page
    * Bugfix: Ignore non-existing levels for a specific domain