Arvados

I thought this would be a relatively straightforward problem, but Peter has dug into it and demonstrated that it's actually much larger, because Workbench makes so many API server queries to render most pages. For the immediate case, we just need to get Collection downloads working with only scoped tokens, and we'll make that happen by creating a separate view to accommodate it (#2764). Any small bugs that interfere with that new view will become tasks on that story.