All normal informational output is now logged at INFO level.
To actually see normal output, the logger is configured to level INFO also.
Log levels:
WARNING is for warnings, ERROR is for (fatal) errors, DEBUG is for debugging.
logging levels must only be used according to this semantics and must not be
(ab)used to let something show up (although the logger would usually hide it)
or hide something (although the logger would usually show it).
Controlling the amount of output shown on INFO level:
--verbose, --progress, --stats are currently used for this.
more such flags might be added later as needed.
if they are set, more output is logged (at INFO level).
also: change strange setup_logging return value
