public class SuppressCache<T>
Cache which keeps a timestamp and counter for every key. When a timestamp has expired (based on an expiry time), the
corresponding key is removed.
This cache is mainly used to suppress identical warning messages (in TP), e.g. if we get 1000 warnings about reception
of messages from P (who's not in our cluster), we can print such a message only every 60 seconds (expiry time = 60 secs).