XML Validation of subsystems

add JBossEntityResolver to resolve imported schema

* XML validation of remoting and threads subsystem
* logging XML can not be validated due to the use of @@ placeholders (the XML validation does not take into account any supplement's replacement)

The pending commits for the wildfly project are at https://github.com/jmesnil/wildfly/commits/xsd_validation_subsystems. I'll open a PR for wildfly with them once wildfly-core 1.0.0.ALPHA15 is released (as some subsystem requires to resolve imported schema)  to be validated).