Tensor binding for not CPU backend

related to #21 (closed)

Actual tensor binding wrap the storage reference as a void * which is too restrictive (according to actual backend, storage type can be anything, possibly larger than a pointer).
Within C++ branch fix/AccessStorage tries to implement a storage management through a future_std::any object but it seems hard to use it with pybind.

Proposed solution: pass to and from python the address of the future_std::any storage object but nether try to interpret its value in python.