Allow group commands to be run synchronously

We have a set of processes we like to put into process groups. We wanted to be able to perform a rolling restart across those processes instead of having them all receive the restart command at the same time. 

I implemented this feature for the dynamically generated commands on the Group class. I could not find a proper place for the configuration settings so I have added the config directives on the Process class.

Hopefully others may find this useful.