create log-dirs if necessary; fallback to syslog

changed semantics of argument to logger: it is really the logfile
(rather than some abstract "name")

is no file is given, log to syslog
if a file is given log to it, and if that fails (because of permissions),
try to do that in /tmp
".log" suffix for logfile-names
new argument "--logfile"
logger.getFiles() might return None