in XmlOptions class, Javadoc for setValidateOnSet() and setDocumentType() should document that these options are also used by the XmlObject.Factory.newInstance() methods

I wanted to see which options were recognized by the XmlObject.Factory.newInstance() methods, but it did not appear to be documented anywhere in the Javadocs. So I dug down into the source and it looks like the only two options that newInstance() recognizes are DOCUMENT_TYPE and VALIDATE_ON_SET (see org.apache.xmlbeans.impl.store.Root's constructor). It would be useful to document this in XmlOptions' Javadocs.