Add loading indicator to the apply annotations file upload

[g1eb]

It takes some time for the file upload request to come back, we need an indicator showing the user that there's something going on and they need to be patient.

[g1eb]

Also need to double check if the annotations get applied if users close the file upload window. We can disable that, however if the user clicks out of the file upload dialog or closes it in the middle of the upload - perhaps they do want to cancel that upload?

[kyao]

I think closing upload dialog would mean cancel, but clicking out side of the dialog would not. Does this seem reasonable?

[g1eb]

yeah, makes sense, we'll do that