Top-level navigation does not show selected state

The Blue Ocean interface does not display a selected state for the top-level navigation. This is especially problematic when plugins add additional top-level links to the interface. Because react renders so quickly it can create a usability problem where the user does not recognize that they have navigated to a new page because the links to do not transition to a "selected" state.

The correct selected state is pictured in the attached screenshot (navigation-selected-state.png) and is already present in the CSS. In fact it's used for run result pages already. We just need to teach React about it for the top links.