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.