Rename @literal to @value

[lanthaler]

Originally raised on the mailing list:

@literal is used to set the value of a property when it is typed or it's language is specified. The name @literal is based on RDF. Something like @value might be easier for JSON developers to understand.

Considering that we have merged @type and @datatype (#31) I think this would make JSON-LD even simpler:

{
   "@value": "2010-05-29T14:17:39+02:00",
   "@type": "xsd:dateTime"
}

might be easier to remember and easier to understand for average developers than

{
   "@literal": "2010-05-29T14:17:39+02:00",
   "@type": "xsd:dateTime"
}

[lanthaler]

RESOLVED: Rename the @literal keyword to @value (2012-01-10 telecon).