2012/09/22: FreeBSD pkgng: pkg_* to pkg cheat sheet

Today I updated my port upgrade scripts (background) to also work with pkg(8), aka PKGNG. This is the translation I used.

The last item is a bit critical, as there is no guarantee that the database scheme stays stable; it works for me with version 1.0 of pkg. It is nothing you would do in a world of binary packages (changing the dependency requirements of an installed package), but it is kind of natural if you think of packages as just a convenient way of tracking which ports you have installed.