It is very hard to see the real values in the postfix queue when they
are overlapping. Having a stacked graph eleviates this whil still
retaining all the necessary data.
If there are more than one postfix running, with separate config file,
and still use the same main log file, this scripts can create stats
split per running postfix instance.
Those scripts have not been tested on the new debian multiple postfix
infrastructure, only on real separate running postfix services.
Except postfix_mailvolume_multi, each plugin needs to be configured per
running postfix.
For mailqueue* it is the config folder name, for mailstats it is the
syslog_name in the config file.
mailvolume is also based on the syslog_name, but can do auto config if
nothing has been set.
