Add classification data to AgendaItem model.
Save Agenda item document classification (AsiakirjallinenTieto)
Ansible: assure app_user can do alter table migrations.
Ansible: run migrations when provisioning.
Import Issue references.

Add reference_text model field to Issue, plus
migrations. Handle missing document classifications.

Final piece of #17.
Merge pull request #22 from tituomin/import-more-data

Import more data