support lambda/function object callbacks

[nevion]

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.

[nevion]

This library: http://www.boost.org/doc/libs/1_59_0/libs/function_types/doc/html/boost_functiontypes/reference/decomposition.html should shorten up get_signatures function significantly.

Here is a demonstration of use with lambdas http://stackoverflow.com/questions/4482646/is-there-a-way-to-deduce-the-signature-of-a-lambda-as-an-mpl-sequence