[editor] Fix DnD element connectedTo property change

Does no longer change the options instead of the connectedTo array. I 
reworked some logic that before only changed the options to now be able 
to handle any kind of string list.

projects/editor/src/app/unit.service.ts

@@ -226,7 +226,7 @@ export class UnitService {
       .subscribe((result: string) => {
         if (result) {
           oldOptions[optionIndex] = result;
-          this.updateElementProperty(this.selectionService.getSelectedElements(), 'options', oldOptions);
+          this.updateElementProperty(this.selectionService.getSelectedElements(), property, oldOptions);
         }
       });
   }