Relay prototype

Considering getting this simple relay implementation into ThaliProject while I finish up the other aspects of it - to simplify folks using the HTML5 seed.   Perhaps into a new branch on ThaliProject - but then you wouldn't be able to see the diff for review.

Only one source file here for the relay - RelayWebServer.java (and RelayWebServerTest.java).  The other bits are all NanoHTTPD.  Open questions on code file headers for those....
Yeah it is a little more complicated as the input stream on the session is the raw socket from the request, so to use it you have to do some HTTP implementation of your own - at the very least checking for content length headers to know how many bytes to wait for.  NanoHTTPD also uses some state recorded earlier in the request to know if it needs to back up in the buffer in some cases during parsing.  I'm going to try something simple and see if it works but my expectation is that at some point I'll overload their HTTPSession and implement one that is better for relaying by offering a stream and length up based on their existing parsing logic.  We'll see shortly :)