userportal,webadmin: brand 404 error pages.

- Fixed broken 404 error page style sheet links.
- Used same styling for 404 error pages as the welcome
page.
- The messages are now brandable and i18ned
- Removed automatic redirect to welcome page.
- Added BrandingFilter that automatically passes branding
information to the servlets.

Change-Id: I3b0406ab6dea4a2cacebd4ad6e62c8bb7a0d44c0
Signed-off-by: Alexander Wels <awels@redhat.com>