Add fromChangeEvents methods to SwingObservable

For swing components which fire `ChangeEvent`s, I added a method `SwingObservable.fromChangeEvents`, similar to the other methods of `SwingObservable`. 

Unfortunately, there is no common base interface for all components which fire `ChangeEvents`s, so I created one myself: `ChangeEventSource.ChangeEventComponentWrapper`.

Then, each component which fires `ChangeEvents`s needs its own overload in `SwingObservable`.

An other approach would be to use reflection, but then we loose typesafety.