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/episode.rs

@@ -110,6 +110,11 @@ impl ListItem for Episode {
         Some(format!("https://open.spotify.com/episode/{}", self.id))
     }
 
+    #[inline]
+    fn is_playable(&self) -> bool {
+        true
+    }
+
     fn as_listitem(&self) -> Box<dyn ListItem> {
         Box::new(self.clone())
     }