Improve support for locking the screen and shutting down system, introduce support for suspend/hibernate

Hello,
I have written some code to enable suspending and hibernating the computer from the rest break window and daily limit window. This was a feature I have needed from a long time. 
By the way, suspend for locking the screen and shutting down was greatly improved. All the actions should work now on most Linux installations currently in use.

Greetings,
Mateusz Jończyk