add package support for OpenBSD

I've been using this for a couple months on my OpenBSD boxes and it seems to work fine. I thought I'd submit it for feedback before I end up sitting on it too much longer. :)

A couple things to call out:

1. The Configurate class makes it a bit easier to deal with config files, and I especially like using it with rc.conf.local and the pkg_scripts services list, but no doubt its not for everyone. Its used for enabling and disabling services.
1. I haven't created any service tests yet.
If we could fit a short comment in here about the difference between PACKAGESITE / PACKAGEROOT that'd be good. I recall long discussions in the past on the freebsd provider. If we can't fit a short comment, it'd be helpful to link to a definitive discussion.