ENH: Add install_from_ppa pillar setting and PPA pkgrepo

On further review, this is more complex to implement than I considered. I apologize.

Does this look correct?:

* False: pkg.install
* True: pkgrepo.managed, pkg.install
* False -> True: pkgrepo.managed, pkg.reinstall
* True -> False: pkgrepo.absent, pkg.reinstall

Is it reasonable to expect an implementer to call pkg.reinstall (install, reinstall=True)