Pass a factory_name in the object_info of monitor and device.
Restructure the factory name to mean something functionaly. With
the factory to library mapping this then means that the implementation
of certain factories can be configured in the config file.
Add signal handlers for daemon to shut down
Add destroy listeners for modules and do cleanup
Fix some leaks
Simplify port registration in new nodes
Hide some more data structures
Let the node implementation take care of the reuse_buffer signal because
then we can get to the graph nodes to find the destination port.
Destroy modules in core cleanup. Modules should undo everything they
have done.
Activate the link after we negotiated format and buffers.
