Improve context menus to make the UX/UI more consistent (#923)

* Add save option to context menu of all possible ListItems

* Add play options to context menus

* Fix for playlists and tracks

* Move playback controls into main menu

src/model/track.rs

@@ -333,6 +333,16 @@ impl ListItem for Track {
         Some(self.clone())
     }
 
+    #[inline]
+    fn is_saved(&self, library: Arc<Library>) -> Option<bool> {
+        Some(library.is_saved_track(&Playable::Track(self.clone())))
+    }
+
+    #[inline]
+    fn is_playable(&self) -> bool {
+        true
+    }
+
     fn as_listitem(&self) -> Box<dyn ListItem> {
         Box::new(self.clone())
     }