Move the zoom levels inside the model

shell/model/Makefile.am

@@ -10,6 +10,6 @@ sugar_PYTHON =			\
 	Invites.py		\
 	Owner.py		\
 	MeshModel.py		\
-	ShellModel.py		\
+	shellmodel.py		\
 	homeactivity.py		\
 	homemodel.py

shell/model/shellmodel.py

@@ -31,6 +31,11 @@ class ShellModel(gobject.GObject):
     STATE_RUNNING = 1
     STATE_SHUTDOWN = 2
 
+    ZOOM_MESH = 0
+    ZOOM_FRIENDS = 1
+    ZOOM_HOME = 2
+    ZOOM_ACTIVITY = 3
+
     __gproperties__ = {
         'state'     : (int, None, None,
                       0, 2, STATE_RUNNING,