Generilizeing pr2_msgs (and potentially other PR2 components?)

I found GPU monitoring feature in pr2_computer_monitor package still functions, on non-PR2 environment despite the naming of the relevant packages. So I filed a suggestion in pr2_common#286 to make them PR2-agnostic, to lower the hurdle of re-using them. It’s easy to fork, rename repos and make releases separately, however I’m not entirely sure if that’s the best approach. Please chime in if this rings your bell.

I have a feeling there’s a lot of components in PR2 that can be generally useful, not just for PR2. I just don’t have much insight thus I started with manageable piece.