Watson region streaming endpoints

[mediumTaj]

The correct streaming endpoint is

wss://stream-fra.watsonplatform.net

Add these checks to WSConnector.cs FixupURL() method and account for and test in other regions.

else if (URL.StartsWith("http://gateway-fra."))
    URL = URL.Replace("http://gateway-fra.", "ws://stream-fra.");
else if (URL.StartsWith("https://gateway-fra."))
    URL = URL.Replace("https://gateway-fra.", "wss://stream-fra.");

[mediumTaj]

fixed in #410