Enhance Administration backend

If one wants to add a child to an existing node using the administration backend, currently there is no intuitive way. In my opinion, the change list view of a model shall use the jstree.js together with the grid library.

This would allow us to render all the fields which should be visible in the list view. It also would allow us to add child nodes using a a special + button or a context menu. Moreover it would allow the administrator to move nodes through drag and drop.