Add property to route that will add the namespace bar to the page.

Currently, the only way to add the namespace bar to a page using extensions is to add the '/k8s' prefix to the path in the route extension. This doesn't allow enough flexibility for pages that require the namespace bar, but aren't k8s resources.

It would be better to add a property to the route to determine whether the namespace bar should be displayed, so that the construction of the path can be left up to the plugin developers.