Add a “wait for all connections to close before switching to sleep mode” mode for idlesleeper

[FRAGM0S]

Currently, each traffic on a service resets the idlesleeper countdown to zero.
I propose adding a mode that doesn't trigger the countdown as long as at least one connection is open with a service.
For example, if I use a service with a static web page, the idlesleeper should keep this service alive as long as the web page is not closed.