userportal, webadmin: added branding cascading resource servlet

- Added BrandingCascadingResourceServlet to serve cascaded images and
other resources outside of CSS.
- Added favicon.ico serving in host page and root page.

Change-Id: I1dcd9d0f22a7c5867c39576020ad16dd6c53deda
Bug-Url: https://bugzilla.redhat.com/997547
Signed-off-by: Greg Sheremeta <gshereme@redhat.com>