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
Work on idle poll
Move node state to the node interface so that we can actually get it in
the sync case.
Add enabled field to the poll event
Work on audiotestsrc
Support to parse configuration files. By default, the default conf file
is parsed ({sysconfdir}/pinos/pinos.conf), but that can be changed with
an environment variable (PINOS_CONFIG_FILE). The file can contain
commands and assignments (no assignment supported this far).
Support for command module-load is added.
