Sort dashbord list in frontend

It make sens to sort in dashboard especially if later we want to have ability to change order (like by date , modified, or active first) without re-fetching the data. Otherwise each content manager should reimplement each sorting logic. 

See https://github.com/jupyter/jupyter-drive/pull/24
This sorts `'directory' < 'file' < 'notebook'`, but we want `'directory' < 'notebook' < 'file'`, don't we?