Merge pull request #1 from terrellt/rdf

Added namespace fixes in tests, .clear functionality, multiple syntax su...
Merge pull request #2 from terrellt/rdf

Rdf
remove controlled vocab tests; this is probably not core AF functionality
Merge pull request #3 from terrellt/rdf

Work Towards Nested Attributes
allow non-xsd:string literals
better handling of rdf subjects
Fixed blank node querying.

Assigning child nodes wasn't maintaing the object that was set, which resulted in a new blank node being created to represent that child node when accessed. By adding it to the node cache that's bypassed, allowing for its rdf_subject to be queried appropriately.