multipart messages

DRAFT Multipart messages

First of all, the rcid idea is wrong. Caller cannot distinguish responses to own calls from tunnel/multipart messages responses. There is request ID clash possibility.

Bi-directional tunnel

1. There is **/tunnel:create method returning tunid as String
2. Upon successful tunnel creation, the **/tunnel/tunid node exists
3. client can sen data to the tunnel calling **/tunnel/tunid:write
4. The tunnel data exchange is started by first **/tunnel/tunid:write call.
5. All responses to **/tunnel/tunid:write are send with request-id of first call, but with increasing SeqNo attribute value
6. Tunnel is closed when:
   1. **/tunnel/tunid:close is called
   2. RpcError message is sent by one of side
   3. There is no traffic for 1 minute
7. Tunnel creation and destruction is signalized by **/tunnel/tunid:ls:lsmod signal