ISPN-3157 + ISPN-2997 + ISPN-3158 

ISPN-3157 Align Infinispan subsystem to match AS 7.2 / EAP 6.1. This means schema bump to 5.3. Also finally enable subsystem testsuite
ISPN-2997 Test for backwards compatibility in the endpoint subsystem
ISPN-3158 Allow configuration of compatibility mode

https://issues.jboss.org/browse/ISPN-3157
https://issues.jboss.org/browse/ISPN-2997
https://issues.jboss.org/browse/ISPN-3158

For the reviewer: ISPN-3157 is really just about aligning with the upstream Infinispan subsystem, so really not much point reviewing, apart from the introduction of the 5.3 parser and XSD (based on the 1.4 model).