Add RDFS for type and attribute pages

Includes properties such as:
* rdfs:comment
* rdfs:label
* rdfs:subClassOf

With this patch, individual type and attribute pages will now express basic
RDFS; classes will express their immediate subclass relationship and all
of the properties that can be applied to them, while attributes express
their domainIncludes values.

Addresses #24

Signed-off-by: Dan Scott <dan@coffeecode.net>