* python/dbus_bindings.pyx.in (send_with_reply_handlers): New send

* python/dbus_bindings.pyx.in (send_with_reply_handlers): New send
method for doing async calls
(_pending_call_notification): New C function for handling pendning call
callbacks
(set_notify): New method for setting pending call notification

* python/dbus.py: new version tuple "version" is set at (0, 40, 0)
Async capabilities added to remote method calls
(Sender): class removed
(RemoteService): class removed
(ObjectTree): class removed for now
(RemoteObject): Renamed to ProxyObject
(RemoteMethod): Renamed to ProxyMethod
(method): Decorator added for decorating python methods as dbus methods
(signal): Decorator added for decorating python methods as signal emitters
(ObjectType): Metaclass added for generating introspection data and the
method callback vtable
(Interface): Wrapper class added to wrap objects in a dbus interface
(Object): Uses ObjectType as its metaclass and exports Introspect
of the org.freedesktop.DBus.Introspectable interface
(ValidationException, UnknownMethodException): new exceptions

* python/examples/*: Modified to fit with the new bindings