Remove Xalan from TomEE

TomEE ships with Xalan 2.7.2 which has not seen an update since 2014. It does not look like any of the components we're using actually rely on it.

Furthermore, it has bugs such as https://issues.apache.org/jira/browse/XALANJ-2617, so making use of an XML Transformer when Xalan is present may mean XML is produced with invalid characters.