Add CheckExpectations function to TMock to ease using Delphi-Mocks with DUnit

When using Delphi-Mocks in DUnit tests, I'd prefer to end the Test procedure with:

  CheckEqualsString('', fMockTest.CheckExpectations, 'Mock Test Expectations');

rather than:

  fMockTest.Verify;
  Check(True, 'dummy check to quieten DUnit');