code: public FastAdapter<Item> withSelectable(boolean selectable) {
          if (selectable) {
              addExtension(mSelectExtension);
          } else {
              mExtensions.remove(mSelectExtension.getClass());
          }
          //TODO revisit this --> false means anyways that it is not in the extension list!
          mSelectExtension.withSelectable(selectable);
          return this;
      }
docs: Set to true if you want the items to be selectable.
  By default, no items are selectable
  
  @param selectable true if items are selectable
  @return this