LP1474874: Consistent page headers in the Angular client

LP1474874: Consistent page headers in the Angular client

This commit ensures that each screen in the Angular staff client uses
the <eg-staff-banner> component to better orient its users.

This commit also gives the eg-staff-banner some <h1> semantics, per
WebAIM's guidance: "Pages should be structured in a hierarchical manner,
generally with one 1st degree headings (<h1>) being the most important
(usually page titles or main content heading)" -- https://webaim.org/techniques/semanticstructure/

To test:

1) Go to [your-server]/eg2/en-US/staff/catalog/search
2) Confirm that there is a header that gives the page title at the top
of the page.
3) Go to an Angular Vandelay page.
4) Confirm that you see a similar header as in step 2.
5) Go to an Angular Administration page.
6) repeat step 4.

Signed-off-by: Jane Sandberg <sandbej@linnbenton.edu>
Signed-off-by: Jason Boyer <JBoyer@equinoxinitiative.org>