changed result of ecapnp_message:read/1
the rpc/vat/cap implementation is taking form.

each remote vat is represented by a running
gen_server (implemented by ecapnp_vat).

all local capabilities are simple_one_for_one
workers of ecapnp_capability_sup.

ecapnp_rpc simply directs traffic to either:
- ecapnp_capability (for local caps) or to
- ecapnp_vat (for remote/imported caps).
add id field to #field{} record.
locally routed rpc (including pipelining) now functional again!
clumsy & clumsy, but a basic restore & call between two VAT's works now!