Allow passing timeouts to the underlying HttpURLConnection

[bipster]

Using the expanded Semantics3 API can take 40 seconds or more. But also even just networking issues could result in a hung connection.

As-is, the HttpURLConnection used to connect to Semantics3 is built and used within methods and not accessible to clients. Perhaps Semantics3Request should accept a constructor parameter to control read and connection timeouts when opening connections.