Feature Request: remaining upload indicator

[OhMaley]

Related to #3022 of the original repo

Below is the original issue to tackle:

It would be helpful to add a progress bar or spinning wheel for bundle uploads, so the user/organizer knows things are progressing.
Using the public instance, uploading both competition bundles and submission bundles take longer than expected, and it's not obvious when it's a connection issue.
A real progress bar would be great, also when uploading files in the "My Datasets" page.