Servervar group

Added the servervar_group case for MatchOrder.
Behaviour: 
- with url path (/de/example/simpelpage) using the url match to define the siteaccess
- for the homepage (eg.: www.example.com) using the browserlanguage send via VHOST variable to ezpublish and redirect to correct path (english: www.example.com -> www.example.com/en)

Usage:

- settings/override/site.ini.append.php:
-- MatchOrder: servervar_group
-- ServerVariableName=SUBSITEACCESS

- vhost: (for example english subsiteaccess)
-- RewriteCond %{HTTP:Accept-Language} ^en.* [NC]
-- RewriteRule (.*) - [E=SUBSITEACCESS:en]