- don't use "hash" for a local variable in python.
  The editor highlights it like a special python name.

- don't use "settings" for Connection.settings. Name it
  Connection.con_hash. The name "settings" is over-used already.
  "con_hash" really is the nested dictionary that we expose/receive
  from D-Bus. If we would use libnm for it, it would be an
  NMSimpleConnection instance, but we don't.