Merge remote-tracking branch 'ansgar/pu/multiarchive-1' into merge

* ansgar/pu/multiarchive-1:
  dak/init_dirs.py: only create directories for active keyrings
  dak/init_dirs.py: do not use Dir::Pool
  change documentation style
  Python modules should not be executable
  daklib/archive.py, daklib/checks.py: implement transition blocks
  daklib/archive.py: use method to decide which policy queue to use
  daklib/archive.py, daklib/checks.py: implement upload blocks
  daklib/dbconn.py: use apt_pkg.TagSection instead of implementing our own parser
  daklib/archive.py: check for source when copying binaries

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