[openwebnet] handle Thermo Central Unit monitoring messages (#12485)

[openwebnet] handle Thermo Central Unit monitoring messages (#12485)

* - handled what=30 (failure discovered ), what=22 (at least 1 probe in off), what=23 (at least 1 probe in protection), what=24 (at least 1 probe in manual)
- related channels added
* - update README
- ignore messages from probes and central unit and keep track only of messages from a real thermostat
* add example of failureDiscovered channel
* Update bundles/org.openhab.binding.openwebnet/src/main/resources/OH-INF/thing/channels.xml
* changed capital letters (atLeastOneProbeOFF -> atLeatOneProbeOff) as suggested

Signed-off-by: Conte Andrea <andrea@conte.com>