Update ServerTracer interface and implementations.

SpanIdImpl is package private like all implementations, so submit
individual trace, span and parent span ids in setSpan method.
Update EndPoint to both have methods to return ip as integer and as string. Also update implementation to have additional constructor that takes ip as String.

Providing ip as string is probably easier for users + we are sure we
convert them in the expected way to int.
Update EndPointSubmitter interface and implementations so ip address is submitted as a String iso int.