XML serializer based on XOM

This adds support for an alternative XML serializer to dom4j.

XOM is an open source (LGPL), tree-based API for processing XML with Java that strives for
correctness, simplicity, and performance, in that order.
http://www.xom.nu/
Minor modifications in XOM converters

Changed XmmToByteArray to XomToString converter and fixed @since in javadoc.

Issue #AXON-232 Fixed