HTML5 Upload Progress (#6177) (#6583)

Authored by machniak on Feb 3 2019, 9:49 AM.


HTML5 Upload Progress (#6177) (#6583)

Replaced all old upload progress code in favour of ajax upload progress.
Instead of posting a hidden iframe, we now use AJAX (as we did for drag-n-drop).
Removed code for old browsers. Now we support IE >= 10, Firefox > 4.
Upload progress may not work in some more, but support is quite good.