configury: re-factor to	extract	common code

Pull common code out of the provider .m4 scripts and back into a
central .m4 file.  Now much of the setup and administration stuff for
FI_<provider>_CONFIGURE is done in a central location -- the
_CONFIGURE macros can just be small chunks of code that focus on
checking to see if that provider can be built (e.g., check for headers
and libraries and that's it).
.gitignore: don't ignore the entire config directory

It's useful to put our own .m4 files in config, so just ignore the
specific Autotools-generated files.
psm: remove outdated use of HAVE_PSM
verbs: remove outdated use of HAVE_VERBS
Merge pull request #154 from jsquyres/topic/moar-configury

configury: re-factor to extract common code