For a TBX Import:

It should be possible to add the value of a text field type attribute to the existing attribute value in the DB, instead of replacing it. It should always be added with "; " (so semicolon plus space) in between the existing value and the value to be added.

For what attributes this should be done should be configurable in the GUI in the pop-up, where you can select the TBX for the import.

There should be 3 new tag-fields to select those attributes, where the values should be concatinated, one for entry level attributes, one for language level attributes and one for term level attributes.

Selectable should be all attributes, that exist so far in the TermCollection in question.

The common header for all 3 fields should be

EN: Merge of attribute values
DE: Zusammenführen von Attributswerten

The common subtitle / description

EN: For existing terms: Merge the values of selected attributes, instead of replacing them.  ("; " willl be added between the merged values)
DE: Für bestehende Benennungen: Die Werte ausgewählter Attribute zusammenführen,
      anstatt sie zu ersetzen ("; " wird zwischen den zusammengeführten Werten ergänzt).

Testdata can be found here: test-data/terminology/test-cases-merge-terms.zip