make album column for tracks configurable

introduces new config variable `album_column`

fixes #267

src/album.rs

@@ -176,7 +176,7 @@ impl ListItem for Album {
         format!("{}", self)
     }
 
-    fn display_center(&self) -> String {
+    fn display_center(&self, _library: Arc<Library>) -> String {
         "".to_string()
     }