core-login: setup login using github account

Notice that compared to the seminars, I am not using the ":" in
applicaiton.properties. For some reason, in our version of spring it is
not supported. If used, it will be ignored, but there would be no
warning or error.

To log in, simply go to http://localhost:8080 and login using your
github credentials, authorize the service to use your information
(specified in scopes) and you will be redirected to Demo page.