Nav and CoNav links should be allowed that are relative to doc root. The url rule in NavigationLink.php and CoNavigationLink.php requires a full, valid url. The user should be able to reference another part of the COmanage app w/out the host, e.g., '/registry/co_people/index/co:2' to navigate to that page.

Also, the option to have the link render in a new window should be added, for example, when navigating to an external site.

Finally, the current validation is misleading in that if an invalid url is entered, the empty error msg is shown.