Initial commit of RAP Hello World skeleton and libs

Google API taken from
http://google-oauth-java-client.googlecode.com/files/google-oauth-java-client-1.17.0-rc.zip
Cleaning up, change sign in button text
Sandbox to experiment with Google login and RAP

- A half complete example where login is triggered from JavaScript shown
in a RAP browser widget.
- A complete and working servlet based example.
- Calling the ConnectServlet in the browser widget directly does NOT
work!

TODO: provide a RAP service handler and call it from the loginFinished
function in JavaScript to transfer the received access_token back to
RAP. Then proceed as in the servlet example to exchange the token for a
long lived rrefreshable token.

! You have to fill the client_secrets.json with apropriate credentials !
Ignore local copy of client secrets.