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....
This is only based on brief observation, but I believe getInputStream will hand you over the socket but not in a way that is useful in an InputStreamEntity (it must have access to the full request or it won't know how to read the body, so we'd have to buffer the earlier parts of the request which we have already read and thrown away, and hand it a full copy of the stream to parse itself).   I'll glance over the java docs a bit to make sure this is the case though.

I think NanoHttpd actually serves as a great little starter-kit to build a nice relay if you implement your own HTTPSession and make it work the way you describe - just was a more significant effort so was starting with leveraging most of NanoHTTPD as is.