Removed unused interface
Added upload css
Revert "Added upload css"

This reverts commit cbd547de1cc300285576751d199e2ab77b63ae44.
Return a white png background instead of 404
Sandbox updated
Logo and background uploading rewrited with image drag/drop (wip)
Changed spinner image
Logo and background uploading rewrited with image drag/drop.
Add new spinner gif missing in previous commit