refactor: every indexable thing can be a favorite

src/things/abstract/saveable-thing.ts

@@ -12,6 +12,7 @@
  * You should have received a copy of the GNU General Public License along with
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
+import {SCIndexableThings} from '../../meta';
 import {SCThing, SCThingUserOrigin, SCThingWithoutReferences} from './thing';
 
 /**
@@ -19,18 +20,17 @@ import {SCThing, SCThingUserOrigin, SCThingWithoutReferences} from './thing';
  */
 export interface SCSaveableThingWithoutReferences
   extends SCThingWithoutReferences {
-  // noop
 }
 
 /**
  * An encapsulation of the data (e.g. a thing) that is saved, which provides additional information.
  */
-export interface SCSaveableThing<T extends SCThingWithoutReferences>
+export interface SCSaveableThing
   extends SCSaveableThingWithoutReferences, SCThing {
   /**
    * The contained data
    */
-  data: T;
+  data: SCIndexableThings;
   /**
    * Type of the origin
    */