MR compilation should validate the contract for MR types

The contract for a MR type is that its public API must be the same across all versions.

Now consider the following situation with the default type be:

```
MRType {

public String sayHello();

}
```

in a further `Version X` becomes

```
MRType {

public String sayHello(Locale locale);

}
```

this would be forbidden because code calling `MRType.sayHello()` will fail when running on `Version X` with method not found.

There should be a check that tell the user about the situation in this case it must complain that the public method `sayHello()` was removed in version X.

Similar things can happen for parameters, return types, fields and so on.