Homematic: Fixed Problem with active binding, use of real item registry.

There was an error in the active binding handling, preventing the binding to recover from CCU connection failure. This is fixed. As already written in last comment, the binding checks every 5min for the connection. If no event from the CCU was received in this 5min, the connection is re-opened.
The next fix is about the usage of the real item registry. Before the items were cached inside the generic item binding in a hashmap to be able to find them by name. That was very error prone in history and still lead to wrong values inside the binding. The binding now uses the real ItemRegistry service.