Severe changes to naming and semantics.

- removed async.object and async.async_object and renamed it to async.Object.
- async.Object.__enter__() is now deprecated (with-context management). The
  the Object.synchronized property should be used instead.
- the autoproperty class got some docs, won't notify on __get__()
- NOTIFY_SINGLE has been renamed to NOTIFY_ONE
- The Box class is now an Object subclass and is no longer a proxy class
- Removed Proxy stuff