Handle multivolume TEI files
As the title says. There may be works that are distributed over several files, e.g. Vitoria's Relectiones:
<TEI xmlns="http://www.tei-c.org/ns/1.0" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="W0013">
<teiHeader/>
<text xml:lang="la" type="work_multivolume" xml:id="completeWork">
<group>
<xi:include href="W0013_Vol01.xml" xpointer="Vol01">
<xi:fallback>
<p xml:lang="de">Band 1 konnte nicht eingebunden werden.</p>
</xi:fallback>
</xi:include>
<xi:include href="W0013_Vol02.xml" xpointer="Vol02">
<xi:fallback>
<p xml:lang="de">Band 2 konnte nicht eingebunden werden.</p>
</xi:fallback>
</xi:include>
</group>
</text>
</TEI>
It would be desirable to have one deposit per-multivolume work containing several XML files...