Eliminate header and rpmte knowledge from rpmfs

Eliminate header and rpmte knowledge from rpmfs

- rpmfs is such a low-level construct it doesn't need to know anything
  about the upper layers. Gather the necessary bits of info in the
  sole caller instead and pass only whats needed to rpmfsNew() to
  enable creating a filestate item without having rpmte/header at hand,
  which we'll be needing in the fsm shortly.