Merge @coerce with @context (#40)

In preparation for today's telecon I've tried to collect all proposals for
issue #40 so far:

1)  "foo": {"@iri": "http://uri.foo", "@coerce": ["xsd:date", "@list"] }

2)  "foo": {"@iri": "http://uri.foo", "@coerce": "xsd:date", "@list": true}

3)  "foo": {"@iri": "http://uri.foo", "@datatype": "xsd:date", "@list":
true}

4)  "foo": {"@iri": "http://uri.foo", "@list": { "@datatype": "xsd:date" } }

5)  "foo": { "http://uri.foo": { "@list": "xsd:date" } }



--
Markus Lanthaler
@markuslanthaler