put persName/ref/text() to persName/@label

[kkrebs]

persName/ref/text() ist missing, we should use the label attribute

<persName type="TMKl-Nef">
  Türabî <ref target="pr-30522253-4">TMKl-Nef/V.ii, p. 224</ref>
</persName>

<mei:name type="TMKl-Nef" nymref="cmo_source_00002620" label="TMKl-Nef/V.ii, p. 224">Türabî</mei:name>

[kkrebs]

I checked if we can use solr index for this. For composer names this works, but for other name sources, like simple bibliography links we still need a label (see http://cmo.gbv.de/cmo/receive/cmo_person_00000377 or pp-21950636-8).