Add callback suport to expectations

I think it would be a lot easier to mock method behavior if method/property callbacks where allowed when recording/setting expectations.

It could be achieved by adding a Callback method to the IMockBehavior interface:

Callback(MockMethodCalledEventHandler mockMethodCalled)

Or by adding ExpectAndCallback and Calback methods to the RecordExpectations class:

public IMockBehavior ExpectAndCall(
    object mockedStatements,
    object returnValue,
    MockMethodCalledEventHandler mockMethodCalled
);

public IMockBehavior Call(
    MockMethodCalledEventHandler mockMethodCalled
);