When enabled this option will timestamp new lines with the time elapsed
since the line before.
This is a very useful feature to identify which events takes the most
time.
Also changes default timestamp format from ISO8601 to classic 24-hour
format as this is assumed to be the format that most users would prefer.
And reintroduces strict but optional ISO8601 format.
This feature allows to easily add more timestamp formats in the future.
But make the timestamp format RFC3339 compliant instead. The RFC states:
NOTE: ISO 8601 defines date and time separated by "T".
Applications using this syntax may choose, for the sake of
readability, to specify a full-date and full-time separated by
(say) a space character.
This way we keep the information specified by ISO 8601 but make it more
human readable which is better for the console output.
We do not need the date part of the timestamp. It simply takes up too
much precious line space. In case of logging to file, one can easily
conclude the date from the file date information.
