ISPN-2860 RHQ plugin should ignore spurious MBeans returned by the AS7 MBeanServer

RHQ plugin should ignore spurious MBeans returned by the AS7 MBeanServer
Add missing displayNames to attributes and operations
Make the RHQ plugin descriptor generator throw an exception if an attribute or operation is missing the displayName

https://issues.jboss.org/browse/ISPN-2860