Add show actions on item

[aome510]

Brief description of changes

• add ShowActionsOnSelectedItem to show a popup containing of possible actions to act on a Spotify item (Track, Album, Artist, Album, Playlist)
• add command::Action to represent an action to act on a Spotify item.
• implement Spotify client handler functions for
  • get current user
  • adding track to a user's playlist
  • save a Spotify item to user's library.
• update the authorization token's scopes to add user's library modify permissions
• replace the use of playlist::SimplifiedPlaylist with state::Playlist
• simplify the init codes to get Spotify data to run the application on startup.
• remove BrowseSelectedTrack(Album|Artist) commands.
• decrease the refresh duration for the player event handling thread.
• small refactors, remove code duplications, etc