Device monitor update rate

[THuckemann]

The voltages displayed on the device layout are updated at a much slower frequency (sometime only every 5 sec or so) than the values displayed in the list below.

[shumpohl]

By default the update interval for the server is about 33ms (minimal_update_delta).

The GUI only gets an update if the server collcted differing parameter values or if 1s (maximal_update_interval) has passed.