* Simplify Header rendering, remove the use of react-slot-fill
* Remove the useless "/analytics" route
* Move all the <Header> renders to the new, declarative way of specifying breadcrumbs
* Re-render the Layout when a report is added using the REPORTS_FILTER, since that affects the breadcrumbs output
* Fix the base breadcrumb link and breadcrumbs on embedded pages
* Expanded Layout.propTypes to specify the breadcrumbs' shape