LP1615707 Skip link for staff navigation

LP1615707 Skip link for staff navigation

A small patch to address one of the issues in bug 1615707. This adds a
skip link above the staff nav bar. When it has focus, it's visible and
sits on top of the regular navigation links. Otherwise, it's placed off
the canvas.

Updated to simplify the routing approach and add a missing page title
(used as the skip destination anchor).

It would be great to customize the text of the link to specify the
context. For example, the bookshare.org search results skip link reads
"Skip to 1 through 7 of 7 search results." That will be more complicated
to implement though, and this wording is a common and accepted pattern.

This patch covers only Angular screens. A separate patch will be needed
for AngularJS.

Signed-off-by: Stephanie Leary <stephanie.leary@equinoxOLI.org>