Add support for more date related methods in XWQL language

Just hit a blocker to use XWQL: I need methods like month(somedate) and year(somedate) to do some grouping based on the date and I can't find any equivalent.

I see theses listed on http://www.datanucleus.org/products/accessplatform_2_2/jpa/jpql_functions.html but they are indicated as non standard. Would their be some extension to activate or something to support them since theses are actually converted to hql most of the time currently ? I think it would be ok to support them or not depending on the storage implementation as soon as it's documented what implementation support what in the XWQL language.