Don't directly expose the state change methods. Only expose an activate
method for nodes that indicates if the node should be scheduled or not.
Let the link automatically negotiate two active nodes.
Make some defines for properties.
Use link property to make passive links. Passive links don't activate
the nodes.
Make sure the mainloop quits when quit is called before run.
Avoid duplicating API, remove implementations from port and node and
always use an spa_node as the implementation, it's just as easy to
implement a spa node. With the implementation always being a spa_node
we will be able to better implement the negotiation of the mixers.
Add some callbacks to trigger push and pull in a graph
Remove the scheduler, make some implementations of graph push/pull
functions.
Add some properties to jack clients and nodes
Fix the parent of the clients.
Notify link format changes
