Allow Dynamic Idle Screen

[anlumo]

Allow integrating a custom idle screen for displaying stuff like public transport departure times or the current time.

[jaeh]

nice idea :)

have a look at 10.20.30.90/timetable when you are in the metalab or loungenet wifis,
2er linie and u2 are working already, the other lines need to be enabled in the slackomatic backend.

also still waiting for the wiener linien api key, 10 days and counting