Send log to stdout and stderr output streams only.

[eoehen]

If we add the parameter (-a) for append the logfile we have no control about the log file size.
We have to think how we can limite the log file size, before we activate this parameter.

• Remove support for write cron log file.
• Support to send log information to stdout and stderr output streams.

Feedback from @pfeigl in #37.

[pfeigl]

Coming from another direction: If the logfile is only created to be able to tail it and show all output in the docker logs, we could instead not create a log at all and write our output to /proc/1/fd/1, which is the stdout which docker connects to.

You can try it with echo "hi" > /proc/1/fd/1 which will just show up in docker logs