reworked to only reflect the changes in CardDAV owncloud, replace original pull request

The CardDAV Backend consits of two changed files and two new files.
the new files are: backend/carddav_oc5.php  and include/carddav_iOC5.php 
the changes were necesary to add one section in each config file:
backend/combined/config.php   and config.php
everything else can be ignored