German OpenNLP NER model "nemgp" has no mapping

Without the mapping, when using the model no sub-NE annotation are created.
This should do the trick:

```
per=de.tudarmstadt.ukp.dkpro.core.api.ner.type.Person
loc=de.tudarmstadt.ukp.dkpro.core.api.ner.type.Location
org=de.tudarmstadt.ukp.dkpro.core.api.ner.type.Organization
#MISC
*=de.tudarmstadt.ukp.dkpro.core.api.ner.type.NamedEntity
```