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....
Is there anyway to just get to the raw URI? The reason I ask is what happens if an incoming URI has a fragment (e.g. #...). That isn't supposed to happen but it could and I'm not sure that this code would do the right thing. Ideally we would just take the URI path as is (I bet there is an API somewhere to get to the raw path) and just append it.