Clean up sugar + NM client interaction

Change "init-failed" signal to 'initialized' so uninitialized
devices don't leak in the sugar model.

Get rid of 'ssid-changed' signal on Network objects, makes no
sense conceptually, plus new 'initialized' signal replaces
what it was used for.

shell/model/accesspointmodel.py

@@ -45,17 +45,12 @@ class AccessPointModel(gobject.GObject):
 
         self._nm_network.connect('strength-changed',
                                  self._strength_changed_cb)
-        self._nm_network.connect('ssid-changed',
-                                 self._ssid_changed_cb)
         self._nm_network.connect('state-changed',
                                  self._state_changed_cb)
 
     def _strength_changed_cb(self, nm_network):
         self.notify('strength')
 
-    def _ssid_changed_cb(self, nm_network):
-        self.notify('name')
-
     def _state_changed_cb(self, nm_network):
         self.notify('state')