change resource data field names to those mentioned in spec

[lotia]

The Learning Registry Specification mentions resource data field names at https://docs.google.com/document/d/191BTary350To_4JokBUFZLFRMOEfGYrl_EHE6QZxUr8/edit?hl=en_US#heading=h.kdtam7-568cce
the plugin should use those instead of the ones we are currently using.

[jasonhoekstra]

Sensing this no longer is an issue now that resource_data is a DC 1.1 message. Looking through the spec, I think we have all of the required elements for a LR 0.23 valid message.