Add a system log of events happening.
Ït is quite cumbersome to get an overview of what has happened just
looking at the screen of the device. So we will build a global system
log of events that we can use and display what has happened.
Display a system log screen after the config screen.
Test fixes for the gui log screen.
Switch to overview after system log.
Use a row number as track-keeper and iterate that backwards then
displaying or we will show empty or wrong lines.
Do not use time as key for showing events or events at t == 0 (boot)
will never show. Use the event_type as trigger instead.