support lambda/function object callbacks

See http://stackoverflow.com/questions/16845547/using-c11-lambda-as-accessor-function-in-boostpythons-add-property-get-sig for possible ideas and discussion

We need a painless - wrapper free way to specify regular old lambdas which support captures - the plain function's yielded with + almost satisfies this but does not support captues

This causes code to be far longer than necessary and from first hand experience, lambdas are much more macro friendly.