This class introduces the `RunningStatistics` class, which allows to
compute the mean and standard deviation of a set of numbers. These
values are computed incrementally and can be associated to a name. The
values computed by `RunningStatistics` can be dumped upon regular
program termination, `SIGABRT` and `SIGINT`. In practice they are
printed at the end of the program execution, even in case of asserts and
`Ctrl + C`. Moreover, `SIGUSR1` is used to trigger printing the
statistics without crashing the program.