Modify libvirt driver to use consistent method names.
Modify list_nodes method in the libvirt driver to it returns all nodes
(including stopped ones).

Also modify other methods to use domain uuid instead of domain id so those
methods also work on stopped nodes which don't have an id assigned.
Add and use _to_nodes and _to_node method.
docs: Add documentation for libvirt driver.
docs: re-generature documentation fixtures.