Add factory and new-style config for Jaeger exporter

[tigrannajaryan]

See OpenCensus exporter factory.go and config.go as an example.

[MohamedElqdusy]

Hi @tigrannajaryan, I'd like to pick this one.

[tigrannajaryan]

@MohamedElqdusy great! Assigned to you.

[pjanotti]

Sorry I missed this one: we need to do this via simple senders, that don't have their own queue and consistently handle service name. The exporter should not be based on the client library one.