Decouple the SPA port ids from the pinos port ids, this allows us to
more easily link and relink things and do dynamic connection later.
Implement multiple output ports on a pinos node.
Make events and command specific to the node
Remove some unused code
Improve state changes
Use easier fixate by just taking the element default value
Fix reuse buffer in the proxy
Remove the port object. We don't use it as a dbus object and we don't
need it, we can use the link and node object directy.
Move poll code and event handler to the node.
Add more buffer types to add and remove memory shared memory between the
server and client. We would like to send buffers only once and then
simply reference them by index.
Do format negotiation and stream start with a START message.
