ModelWrapper: change model after instantiation

[sideisra]

The ModelWrapper operates on the model instance that has been passed when calling the constructor. In some cases it would be great to be able to exchange the model isnance with a new one.

Example:
In a client server scenario the client shows a model instance loaded from the server. Later the client updates the model because other clients have changed the data by loading the data an creating a new model instance. To show the updated data we have two options at the moment:

1. Reload the view and reinitialize all bindings including the ModelWrapper.
2. Copy all data from the new model instance into the old one and call reload on the ModelWrapper instance.

It would be great when ModelWrapper would support the following third option:
3. call setModel and then reload on the ModelWrapper instance