1. all log messages will be terminated with \n, whether the user provided
it or not.
2. remove a bunch of print() calls from scripts to reduce clutter
3. replace printf calls with log_* calls to reduce clutter
4. add the new release preview script
http://bugs.eressea.de/view.php?id=1675#c5240
new setting "rule.reserve.twophase" reserves from self first, before reserving from others.
fix a crash when trying to flush logs and there is no logfile.
