Create a shutdown consumer object for every --register activation

Create a shutdown consumer object for every --register activation

On receiving a --register command line, or a call to the Register()
method, the legacy app handler will create a shutdown consumer object
(although it will not register it with the NSM yet). When something
(e.g. the NSM) tells the shutdown consumer to shut down, it emits the
signal "shutdown-requested", which the Legacy App Handler listens for.
The Legacy App Handler responds to the "shutdown-requested" signal by
calling the boot manager's Stop() method.