webstaff: add server administration page

webstaff: add server administration page

This patch adds a landing page for Server Administration and
code to embed all of the admin pages available under Serer
Administration in the XUL staff client.

TODO:

* fix the permission groups editor so that it works
  when embedded in the web staff client
* refactor admin/local/app.js and admin/server/app.js to
  unify some of the copy and pasting
* replace the embedded legacy OU editor with a new
  angular one
* fixes some CSS issues that make text hard to read in
  a few places

Signed-off-by: Galen Charlton <gmc@esilibrary.com>