Change Report client UI to put all reports into the same drop-down

[vteague]

The UI for (IRV-upgraded) Report download currently has a rather clunky separate pair of buttons for getting the assertion reports (json and csv). It'd be nicer if those two were incorporated into the existing drop-down.

This would require dealing with two technical matters:

1. Currently, colorado-rla calls out to raire for those reports, which is fine if the internet connection etc is working, but might be an annoyance if someone has turned it off since assertion generation. It'd perhaps be prudent to do them last, because unfortunately at the moment if one audit report fails, nothing after it seems to run.
2. Currently, raire-service returns a zip of each thing (either a zip of all the csv files, one for each contest, or likewise for json). I guess if we do nothing we get a zip inside a zip, which probably works but isn't great. Perhaps the best thing to do is unzip the zip, incorporate it into the AuditReport folder as a subdirectory, and then zip the lot.