IntroducingErrors - adding trace_level::errors value

Adding an additional class of log message for errors. Changing current log messages to errors where applicable. Qualifying log entries with the class the message belongs to.
It's not perfect but the qualifiers have different lengths. On the other hand it logs are much easier to read if the actual entries start in the same position. I thought about using some kind of acronyms but decided not to (state change is the most problematic (st8chg :smile: ?)). For now I would like to leave it as is - at least until I see a bigger log file. (Also comparing to the remaining work this does not seem very high priority).