[imaging_uploader] Form freezes when uploading a big file

[nicolasbrossard]

I tried uploading a file that exceeds the max upload size set on cbigr-test.loris.ca (2G). The upload got to 1% but then the form froze...I saw this in the JS console:

Failed to load resource: the server responded with a status of 413 (Request Entity Too Large)

This bug occurs both for large candidate scans and large phantom scans.