Avoid NullPointerExceptio. When the user is not a teacher lookup the department via the employees working place.
BibliographicReferences is now immutable
Minor change:
- corrected the resource bundle to the correct one
Bug fix:
- when merging 2 execution courses, if there are persistent groups
associated with the origin, keep the origin along with the groups and
disconnect from everything else.
Merge pull request #498 from cbartol/bugfix/biblio-references

BibliographicReferences is now immutable