Metrics

Initial stab at metrics, more to come later.
 - number of http/net connections & connections by remote address
 - number of http requests (client & server) and requests by uri (only for server)
 - http request latency and rate (client & server)
 - net/http bytes read/written. For http we only record the content/body. So this excludes headers and such.
 - number of event bus & handlers by address
- number of verticles & by verticle type (verticle.getClass().getName()).
For client currently, yes. The URI for client can include query parameters and can be rather long and ugly. I'm not sure if people want timings etc for every http method and/or URI. I wanted community feedback here.