let reseacher group read researchdb password file

- add a researcher group in yaml (useful anyways)
- let it read a password file for the researchdb
  (until we use a gpg based solution)

- in lieu of adding a group the old way in I0964a4c319ce

RT #7105

Change-Id: I9c63c560f42223cac704004f98951b98103d8f33