move sanford config and hosts util classes into their own files

This is just a reorg of this logic that formalizes it a bit.  This
is prep for adding new features to the config class.  This is also
gets these classes more up to our convention of formalizing logic
like this in its own file.

@jcredding ready for review.  No behavior changes just reorgs.  I'm realizing this "Hosts" set business may be going away once we address #92.  Doesn't really matter right now, just observing this.