EnvironmentSpecification returns XExpression

Change-Id: Ic491e4d51450ad48f80f8e32d1be2a42d3432f42
generalized grammar rule for EnvironmentSpecification

Change-Id: Ifae710da5ffec1cffc837ada8dff351ab00c532e
expect RuleEnvironment type for EnvironmentSpecification

Change-Id: I9271109b1f2283453211060b873b0955d95f2301
another test for environmentComposition

Change-Id: Id3809cff4082b73bb52e89656312ae17ef20da2c
simplified validation of ErrorSpecification

Change-Id: Ib7d3df1e7de232feb1be6822731f1c059927933c