Separate the session manager in a monitor and policy part.
The monitor manages the devices and endpoints.
The policy watches the nodes/ports/clients and applies the policy
of linking them.
Because both now have a separate connection, we can remove some
hacks in the protocol. When a remote was both the implementer and
user of an object we could get in a deadlock when the user was
blocked waiting and the implementator was blocked sending a reply.
We used to un-busy a client when it was expecting a reply from a
ping or sync for this reason.
Add and use some more keys for the endpoints and streams.
