Adding import for with_statement (Python 2.5 support)
Implemented and integrated group commands
Small fix for UnboundedVariable when subprcess.Popen fails
Removed --select and --restore options from "register"

This options are replaced by the "group" series of commands.
Added documentation for "mu group" commands.
Adding command-line help for group command
Removing shell=True because otherwise it won't work on Linux
Merge branch 'group-command' of https://github.com/nicoddemus/mu-repo into group-command-nicoddemus-pull-request
Merged group actions.
Making acp serial if specified.
Minor