pulp-dev.py installs and uninstalls packages.

I was on the fence about this. There are still some commands you can perform with manage_setup_pys.sh that you cannot do with this change. I'm not sure whether people use it for that or not, however. Also, I wanted to spend as little time on this right now as possible.

I'd be in favor of considering this further in the future, but for now I'd like to make this change as minimal (and quick!) as possible.