First take at pluggable file attribute + dependency extraction system

First take at pluggable file attribute + dependency extraction system
- move most of the hardwired classification logic from rpmfc C-code
  to macro-based configuration, supporting drop-in addition of arbitrary
  new attributes + dependency extractors based on regex matching of
  libmagic file types and paths
- just the initial rough conversion of our built-in dependency types,
  various open questions + todo-items remain, plus likely fair amount
  of more-or-less subtle breakage