cally: Allow memory management for actions

cally: Allow memory management for actions

Adding an action should allow passing a user data pointer, and have a
notification action that gets called when removing the action. This
allows introspection and language bindings to attach custom data to the
action - for instance, the real callable object that should be invoked.

http://bugzilla.clutter-project.org/show_bug.cgi?id=2479