Enable configuration of verification behavior

[nipafx]

If the XMLs define a schema, the default behavior of JAXP is to download it, use it to verify the XML and explicitly specify default values for all unspecified attributes in the generated output.

Under the assumption that this behavior can be configured for the employed JAXP-classes (e.g. to forego schema verification or explicating default values), it would be nice to allow to pass the rtelevant parameters to XmlCombiner.

PS: Nice lib! Small and just works. 😄

[sentinelt]

I think it can be done currently by specifying custom DocumentBuilder with custom EntityResolver. One of the XmlCombiner constructors allows you to specify custom DocumentBuilder, see the javadoc.