Client: refine UI for audit report download

[vteague]

With #137, there's a basic UI for allowing the state to select and download all the reports, including the IRV reports. This is pictured below.

It's fine, but slightly clunky. Consult with CDOS Elections about whether they'd like it more succinctly packaged.

It's worth keeping the raire-generated reports (the assertion reports, both json and csv) algorithmically separated from the others, because they will block if there's a network issue between colorado-rla and raire.

Also, I added a "Download all" button - check that this is wanted.

[vteague]

It looks a bit odd that the menu is transparent and the numbers from the table below show through. I doubt this is a high-priority issue though.

[vteague]

Done with #91 , #96 and #137.