Merge commit 'mhy/master' into merge

Merge commit 'mhy/master' into merge

* commit 'mhy/master':
  update import_keyring
  now we don't need the dm flag
  allow for keyring priorities
  implement key acls
  add keyring defaults
  tidy up and add more methods to SQLA objects
  add basic mapper classes for new tables
  add acls to database schema
  fix indentation
  move check_status to daklib/queue.py
  move recheck logic into daklib/queue.py
  remove unused code (moving to process-holding) and readd security support

Signed-off-by: Joerg Jaspert <joerg@debian.org>