Removed LoadModule directive configuration. Refs #2074

This fragment is no longer needed as the required modules are loaded
by default; see #1937.
Expose SOGo through custom virtual hosts. Refs #2371

Any hostname listed in sogod/VirtualHosts prop is expanded to an
Apache virtual host configuration. The default host name is always
added to the list.
Added ProxyPass /principals directive. Refs #2221

Carddav client on iOS 7 ignores manual url configurations queries
/principals.  This redirect the request to the right URL.