build a file list for checksums-foo fields. Don't use float() to
compare formats, because Format: 1.10 should compare greater than
Format: 1.9 (use "1.9".split(".",1) and tuple comparison instead)

* dak/process_unchecked.py: check_md5sum becomes check_hashes
and check_hash. If changes format is 1.8 or later, also check
checksums-sha1 and checksums-sha256 for both .changes and .dsc.

  defined, if there are only keys defined we want and also the types
  of the various keys.

implied for non-dak users)

some display tidying

        Add --use-sudo option. Use fcntl locking for writing.
        Move writing into a function (write_transitions).
        Reinvoke self using sudo and --import if necessary.
        Move temporary file creation into a function, use mkstemp.
        Rename to "dak transitions".

   edited file back in place
   (check_transitions): Use proper locking and also use sudo to copy
   the new file in place

generic extension helpers into daklib.extensions

pass the old function as an argument to the new function

functions in dak modules; add upload blocking for dpkg.