move #rpc_call{ params } from module ecapnp check to the ecapnp_get/ecapnp_set modules.
Cleanup list ref code.
fix support for packed struct lists.
Capabilities should always be represented by a #object{} with a #ref{} to a kind of #interface_ref{}.

Fixed setting unnamed union when value was a group type.

I feel it is much truth in that I don't fully understand what I am trying to solve,
until I have solved it at least once.
calculator client add/subtract test passes :)
Add calculator sample client implementation.

Tests literal expression, add and subtract, and pipelining.

N.b. currently ecapnp implementation is not pipelining properly,
as all calls seems to be serialized..