Auto pointers builder

This has !240 (closed) and !235 (merged) as prerequisite.

Simplify the generation of auto-pointers using C++ std::unique_ptr by defininig a template based class that can be used for generating smart pointers for C classes. So removing a bit of duplicated code, error prone and making easier to define new smart pointers on the fly.

One thing, while there's no problem in this case, in general it would be always better to use composition more than inheritance for stl containers.