Zipkin Exporter send service.namespace as Zipkin tag

[cijothomas]

As per spec, service.namespace resource should be sent as a Zipkin tag, and not as service name.

Zipkin exporter currently concats the namespace with service name, and is not sending namespace as a Zipkin tag.
https://github.com/open-telemetry/opentelemetry-dotnet/blob/master/src/OpenTelemetry.Exporter.Zipkin/ZipkinExporter.cs#L140-L142

[eddynaka]

For zipkin, we have two endpoints:

1. localendpoint: the servicename is equal some name that you specified, for example, Zipkin Exporter
2. remoteendpoint: the servicename is equal to the url.

If we switch to tags, what should be translated? the zipkiin exporter or the url?
And, when we convert to json, we have two properties, local and remote endpoint. Should we remove the servicename from those? If yes, RemoteEndpoint will be blank.