The current Red Hat config allows to set DefaultCharset to a value.
In certain situations it is necessary to leave it unconfigured thouguh.
Make the content optional, if the value of apache.default_charset is None,
the item is skipped. Otherwise it defaults to UTF-8.
The docroot fix from PR#240 worked fine for default servers.
But as soon as one uses vhosts this broke as the vhosts were
created under the docroot in /var/www/html rather than the better
/var/www.
Fix this by differentiating between docroot and wwwdir.
Further allow to override both in Red Hat-style configs.
The override allows to reuse this formula for the softwarecollections
rpms.
