WFLY-3189 - validation errors on schema 



The ejb schema fail to validate properly in eclipse. Setting of schemaLocation confuses the XML Catalogs. Setting schemaLocation when importing a namespace is also not portable unless the schema exists in the same folder.

This PR also adds a schema file jboss-ejb-clustering_1_0.xsd who's namespace is declared in an online jboss ejb3 example, but does not exist in any existing schema. If the example is intentional, a new schema (such as provided here) should be added to the release. If the example is out of date, this second commit should be rejected and the online example should be fixed.

@pferraro IMHO just fixing the WFLY8 and WLFY9 doc pages to remove the reference to this schema is fine. I'm not aware of this schema being imported into any other still-valid schema, so the only reason for it to exist is we have docs telling people to use it. Rob's description of this PR says that's fine with him too.

Or are you asking about removing support from parsers as well? I don't have a strong opinion there. All I care is EAP 7 vs 6, not WF 9 vs earlier community versions. Is it better to silently ignore the "clustered" element in an EAP 7 user's DD? Or is it better to fail and inform them that their config isn't doing what they think? What are the odds a user would have this in their DD but end up not getting the behavior they expect? If it's really low, easing their migration task by not making them change their DD is better.