WWW-Static: add static Apache error pages

To be used with:
    cp -R ~rapid/rapidconnect/configuration/apache/static /var/www/html/

And Apache config:
    <Directory /var/www/html/static>
        Options -Indexes
        ErrorDocument 403 default
    </Directory>
    ErrorDocument 503 /static/SystemOutage.html
    ErrorDocument 403 /static/SystemOutage-noadmin.html
    ProxyPass /static !

    # Make use of favicon.ico deployed in static.
    Alias /favicon.ico /var/www/html/static/favicon.ico
    ProxyPass /favicon.ico !