Restored createDocument method
Created by: rvillido
This modification restores DSSXMLUtils.createDocument method that was previously removed as "dead code" in this commit https://github.com/esig/dss/commit/fbe0367274c00c8d1ec94910e0e0459898488f4e#diff-bfe9571bf75caeaed6e15fe89a173d70L751
We use that method to transform XAdES XML document into byte array. It would be good if it could remain in DSS.