2 - implement package priority (for things like Debian's pin feature)
4 - merge SUSETAGS_FILE_* and REPOSITORY_REPOMD_* keys into REPOSITORY_RESOURCE
8 - deal with DIRSTR entries having dirid 0 (for source rpms)
12 - forcebest pruning is not optimal: it should keep multiple packages
13 with the same version instead of reducing to just one package for
18 drop SEARCH_FILES and add SEARCH_BASENAME instead?