Progress: Initial setup for granting init program the ability to handle shutdown...

Progress: Initial setup for granting init program the ability to handle shutdown/reboot.

The standard shutdown/reboot/ctrl-alt-delete process actually operates via interrupts.
Make the init program interruptible by default and add notes in the help.

Add additional callbacks.
The help callback is added to print additional information specific to the init program.
The process thread signal is going to be a new callback that the init program can use to define custom behavior.
This custom behavior will utilize the special shutdown/reboot/ctrl-alt-delete signals.
The init program will be handling more signals than the controller program.
(I may want to consider looking into supporting more signals for the controller program as well.)