Allow any entity in DraggableViews::getIndex()

I don't believe we should be calling the _entity function. ✨ Support identifiers other than nid Needs review solution is better. Closing as duplicate.

istryker → closed merge request !43

I know it's bad form to comment on closed issues. However, this issue still affects the current release.

So, here's a re-rolled patch for 2.1.4, pending a release that incorporates ✨ Support identifiers other than nid Needs review