modules: services: add idle shutdown

This adds a timer that checks if a user is logged in every minute (with a random delay). If a user isn't logged, it logs the time. After 10 minutes, the script searches for 2 machines that will stay up. If the machine is not one of the two, it shutdowns.

Reason for this change : reducing energy consumption of unused computers running 24/7 in the school (better for the environment and reduces cost).

Why we want to keep some machines up : we always need to have a machine up in each room to be able to remote into it and access the layer 2 network of the room. This allows us to wake on lan other machines remotely.