Release 6.20.0: New bundles for support of CalDAV and CardDAV

[changerequest]

4 new bundles:
- c.o.webdav.acl
- c.o.webdav.directory
- c.o.caldav
- c.o.carddav

4 new configfiles:
- c.o.caldav/conf/caldav.properties
- c.o.caldav/conf/contextSets/caldav.yml
- c.o.carddav/conf/carddav.properties
- c.o.carddav/conf/contextSets/carddav.yml

Necessary configuration changes as well as instructions how to get this working for the enduser can be found here:
http://oxpedia.org/wiki/index.php?title=Caldav_carddav_Bundles