Use the v4l2 monitor to dynamically add and remove nodes.
Use the info from the monitor as parameter for the factory init and use
it to configure the new node.
Add info to the node.
Use info from the factory as properties on the PinosNode
Keep state variable to enumerate things. This allows us to remove the
expectation that the same index will give the same item.
Use a new rectangle type for video size. When enumerating sizes, this
allows us to specify relations between width and height more easily.
Remove the struct and bytes type, they are like pointer.
Add filter to enum_formats to speed up enumerations.
