Quickfix for adding @Override to a role class

[stephan]

Now that the compiler wants an @Override annotation for each role class that overrides an inherited one (#176), the quickfix for adding this annotation should be extended to apply to role classes, too (currently applies to methods only).

[stephan]

Implemented in r19758.

Only small adaptations to the existing quickfix were needed:

• connect to new problemID (done in QuickfixProcessor + avoid double checking in Java50Fix.createAddOverrideAnnotationFix)
• adjust Java50Fix for handling RoleTypeDeclaration where a TypeDeclaration is expected.