Mbot7 specific setup

If you're setting up mbot7, beware that we have different branches for it. We need to find a better way to handle this.

In mbot_description, do git checkout kinetic-mbot7. Be aware that when doing update_workspace it will print an error message for this branch because it expects kinetic, but you can do it manually.

In mbot_drivers, do git checkout kinetic-mbot7. Be aware that when doing update_workspace it will print an error message for this branch because it expects kinetic, but you can do it manually.