[core] Disable debugging if "-d" is not specified
[core] Disable debugging if "-d" is not specified

Do not print any debugging messages unless "-d" has been specified on
the commandline.
Also, introduce two "special" logfiles "stdout" and "stderr" to log to
stdout and stderr, respectively.

fixes #213

tobi-wan-kenobi/bumblebee-status,tobi-wan-kenobi/bumblebee-status