Reading dc-fw-version is somehow complicated ...
Id does not work reliable on startup, so we do read it also on every
diagRequest().
Version string is then stored in persistent data.
This data can be used e.g. by other tools to show the
device-controller-firmware-version.
- allways check for whole system state (all errors / warnings)
-> e.g. an error does not hide an other error or warning
- send machine event only once
- store sent events in a QSet-container
- clear this container if no error / warning is detected
Note: there is currently no message for releasing a certain single error
/ warning. So it is no worth in removing a single entry in
QSet-container. This is a task for later program versions.
