Processing order for language tags and datatypes

[msporny]

From Ian Davis:

For this markup, what would be the triple generated:
{
"#": { "label": "http://example.org/label",
"xsd": "http://www.w3.org/2001/XMLSchema#"},
"label": "foo^^xsd:date@en",
}

[msporny]

This should probably be the output:

_:bnode1
   <http://example.org/label>
      "foo"^^<http://www.w3.org/2001/XMLSchema#date@en> .

I think we have to have a rule that says that the processing order is "search for typed literal first", then "search for language tag" when determining whether you have a typed literal or a plain literal w/ a language tag.