ifcfg-rh: allow handling complex routing rules via dispatcher (rh #1160013)

ifcfg-rh: allow handling complex routing rules via dispatcher (rh #1160013)

If a connection has an associated "rule-NAME" or "rule6-NAME" file,
don't try to read in the routes, since NetworkManager won't be able to
parse them correctly. Instead, log a warning that they will need to be
applied via a dispatcher script, and provide a script that would do
that in examples/dispatcher/.