Navigation Highlighting

[emartinez-usgs]

Implement navigation item highlighting so the current page is rendered visibly different from other links. For router links, add routerLinkActive="some-class" in the HTML template, then .some-class { /* some styles */ } to the CSS. Unclear how to handle HREF links, but maybe that is for a later date as HREF links should take visitor away from application and thus should never be highlighted (by current application).