Improvements for NodeValue

[afs]

Have less reliance on jena-core Node_LIteral values (LiteralLabel). See also #3558 "Lazy evaluation of literal value".

1. Cache of node to NodeValue creation.
2. Rework the node to NodeValue code in _setByValue to use a map of datatypes to creator functions - this will make any future migration away from using Node values (which are primarily for supporting the Jena Model API and working with java value classes, whereas SPARQL is XSD evaluation).
3. Support date/time long years (beyond an int value) -- jena-core uses java.util.Calendar (legacy).
4. General code tidyup - the code is quite old.