Add Jetty connector metrics

[tomakehurst]

It's often useful to see how Jetty's connectors are performing, in terms of connection counts and inbound/outbound traffic throughput.

So I'd like to propose adding a meter binder for these metrics. I'm happy to contribute a PR for this (I have some tested code already available).

[checketts]

Sounds like a good idea. Are you able to gather these metrics via the JMX Beans or is there a better mechanism?

[tomakehurst]

It just wraps a ConnectionStatistics object, which I think is a "managed bean" as far as Jetty is concerned. Not sure if that automatically makes it a JMX bean, but no JMX APIs were needed in this instance.

[tomakehurst]

Anyway, I'll put a PR your way shortly if you're happy with that.

[shakuzen]

Anyway, I'll put a PR your way shortly if you're happy with that.

Yes please. Thank you.

[tomakehurst]

#1715 - ready to roll now that the Tomcat test fix is merged.