Add sweep to breadcrumbs on snapshot page

If a snapshot belongs to a sweep, we add a link to that sweep in the
breadcrumbs. This helps navigation and makes it more consistent.
Limit width of individual breadcrumb items

The breadcrumbs had started to get really long in some cases. I made
them overflow to an ellipsis at 200px. Yes, we loose some precision. But
breadcrumbs shouldn't be the goto-place for correctness and verbosity,
so I think this works just fine.