Merge commit 'lamby/master' into merge

Merge commit 'lamby/master' into merge

* commit 'lamby/master':
  Drop the SourceFormat-specific validate_format classmethods.
  Don't validate a .changes Format as a source package version format (!)
  Add validate_changes_format utility.
  Move parse_format tests to test_formats.py
  Move parse_format into daklib.formats
  Remove X-Katie: headers
  Updated
  dinstall
  Background half of dinstall
  Dont do work without a tagfile

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