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....
Unfortunately we can't rely on +1 since that port could potentially be taken. So what we need to do is launch the TDH on a random port and then on Android use intents and on the desktop use a config file in a well known location to find it's port. In the case of the relay we can use a file both in Android and Java since the relay and the web browser are run under the same user's account. Probably easiest if the file is .js and just sets the values directly when loaded.