Metrics refactoring

[surik]

Add client metrics and refactor server side metrics for collecting it per listener.

Hello collects the following metrics via exometer_core and reports it to the each registered reporters:

• [hello, server, Name, packets_in, size] - histogram. mean and max size of incoming packets on Name server.
• [hello, server, Name, packets_in, per_sec] - spiral. Incoming packets per second on Name server.
• [hello, server, Name, packets_out, size] - histogram. mean and max size of outcoming packets on Name server.
• [hello, server, Name, packets_out, per_sec] - spiral. Outcoming packets per second on Name server.
• [hello, server, Name, requests, ReqType, per_sec] - spiral. Requests per second on Name server with type ReqType.
• [hello, server, Name, request, handle_time] - histogram. mean and max time of handling one request on Name server.
• [hello, client, Name, requests, ReqType, per_sec] - spiral. Request per second on Name client with type ReqType.
• [hello, client, Name, request, handle_time] - histogram. mean and max time of handling one request on Name client.
• [hello, client, Name, ping_pong_latency] - histogram. mean and max time between ping and pong internal messages.
• [hello, services] - counter. Counter of all available services.
• [hello, bindings] - counter. Counter of all available bindings.
• [hello, listeners] - counter. Counter of all available listeners.
• [hello, clients] - counter. Counter of all available clients.

Name - server or client name ReqType - ok, error, internal

[GalaxyGorilla]

:+1: