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....
Wouldn't we get more 'bang' for the buck if we used an actual HTTPClient for the test? That way we are testing from the wire in. This way we skip the wire completely and wouldn't detect any bugs around things like chunked transfer or inappropriate headers or whatever. If you switch to rest-assured then you get this all for free.