Maximum number of requests and request/second

[lfoppiano]

After several weeks of investigation, I finally found a rather clean solution for implementing a mechanism for limiting the number of requests, using directly dropwizard:

• QoSFilter: Example here allows setting the maximum parallel connections
• DoSFilter: allow to set request/seconds and other mechanisms to protect the service.

Both return 503 by default, so no need to implement such a mechanism by hand.