Add test to document error.
Fix pdf task-listing export.
Use sql-query for dossier-details task listing.
Remove dead code.
Use integer sequence numbers in globalindex.

Make sequence_number not nullable.
Drop latex listing adapters in favour of good old basic classes.
Add column object for latex listing.
Improve column object, add default getter implementation.
Fix dossier cover view when client_title is empty.

Fixes #452.
Merge pull request #451 from 4teamwork/deif-latex-listings

Fix latex listings