We now keep 3 measurements internaly. If a delta is calculated and is
negative, it is ignored. If no delta can be calculated between the
3 last measurements, the last valid response is returned instead, until
a new delta can be calculated. When a cached response is reported, it 
will be logged with a timestamp, name of the counter and all 3
measurements ordered by age (youngest first).
Improved logging with timestamps also for exceptions.

Christian Gerdes authored 2019-02-20 13:52:10 +0100