added link to owncloud/documentation for distinction (#967)
added link to owncloud/documentation for distinction (#967)

Added reference to owncloud/documentation to make it easier for people that want to contribute to the doc.owncloud.org part of owncloud.org.
owncloud/owncloud.org,owncloud/owncloud.org,lefherz/owncloud.org,owncloud/owncloud.org,lefherz/owncloud.org