better way to convert between Python dicts and nvlists (in and out)

[avg-I]

Currently a programmer has to use nvlist_in and nvlist_out that introduce Python objects corresponding to C nvlist_t objects (or placeholders) to a local namespace.
It would be better to use a proxy object that would transparently convert the Python dict arguments as
necessary that invoke a proper C function (via cffi) passing appropriate nvlist_t * and nvlist_t ** arguments to it. cffi provides necessary introspection tools to find out which arguments need translation.
An example of this idea could be seen here: ac179a2