followup on bgruening#1316 which was
not deployed

- use the same chached data for chached and cached_to_index
  i.e. now they differ only in that the later uses the dbprep macro

  if I get it right previously the datamanager precomputed indexes
  which could be used. this seems not possible anymore

  I suggest to leave the dm untouched (than the provided data will also
  work for old sortmerna versions)

- fix usage of cached data (did not work for multiple provided values)
  and add tests

selects default to optional="true" which should not apply here.
also checkboxes do not work therefore.