uapt: Ignore missing SHA1, only show limited missing files
uapt: Use pickle/bz2 instead of anydbm

Results in ~1/10th file size for the packages db. I've also tried using
dbm with bz2'ed values. Compared to the now implemented method, this
 ++ makes starting uapt much faster
 -  makes the lookup process slightly slower
 -- makes database generation much slower
 -  doubles the file size (to 1/5th of the original size)