Improve check for node.js in examples. Add mechanism for clients to increase stack as well as total memory - NB this feature requires emscripten fix only recently applied to incoming so may not be available in SDK yet

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/fadams-javascript-binding@1627942 13f79535-47bb-0310-9956-ffa450edef68