Add protection in DsXmlDeployer to prevent from loading xml resource

If we place a datasource.xml in a jar file, the class DsXmlDeployer will fail with "URI not hierarchical error", because it doesn't handle jar file.
The goal of this issue is prevent for loading jar file in DsXmlDeployer.
The second goal is to provide ability of overring DsXmlDeployer in custom deployer who extends this class.