Move XSLT stylesheets and core XML descriptors to opendj-config-maven-plugin:
* rewrite Maven plugin so that it performs XSLT transformations itself rather than delegating to the xml-maven-plugin. This is required in order to be able to access the stylesheets and core descriptors within the plugin's classloader
* remove dependency on Xalan-J in XSLT transformations since https://java.net/jira/browse/OPENDS-2296 seems to have been fixed, at least in OpenJDK 6u27 and OpenDJ 7u25
* re-enable build of opendj-config, opendj-server, and opendj-server-example-plugin.
TODO once the new Maven plugin has received some more testing in Jenkins:
* add XML validation
* fix support for Windows file names
* simplify code.