[WFCORE-35] Take schema version into account when parsing jvm element.

Also single entry point to JvmXml.java to allow single point for a version switch.
[WFCORE-33] Correct http-upgrade parsing with respect to 1.x and 2.x schemas.
Adding version 1.6 of the schema.
Further changes
A little bit more
HostXml Finished
Switch JVM version switch to be based on major version.