Made PAV links resolve to html page as per https://openphacts2011.atlassian.net/browse/DOC-174?jql=project%20%3D%20DOC%20AND%20assignee%20%3D%20currentUser()%20AND%20resolution%20%3D%20Unresolved
Added discussion about linking to non-RDF datasets to resolve issue https://openphacts2011.atlassian.net/browse/DOC-164