* dfeet/_ui/wnck_utils.py: encapsulates libwnck
* dfeet/_ui/busnameview.py(BusNameView.__init__): add new column for icon
* dfeet/dbus_introspector.py
  (BusName.get_icon): use libwnck to get the icon based on pid
  (BusWatch): add ICON_COL column
  (BusWatch.on_get_value): return icon when requested