cubicweb #320279 running wheel while loading file hierarchy [open]

when one clicks on a folder name in the file hierarchy box, it can take some time before the result shows and the user may think the app blocked.

  1. after the click, insert a running wheel
  2. make the asynchronous call to retrieve data
  3. when data has arrived, replace the running wheel with the result
done in<not specified>
closed by<not specified>