[Issue #36] Adding a screen to get the session id between the login screen and the moment you start making questions

This pull request depends on the following issue: https://github.com/SMILEConsortium/smile_teacher_android/issues/36

The session_values.xml gets the teacher name, session title, and group name.
Then, I send in a JSON request all the values to the url <ipNodeServer>/smile/createsession
There is a session_values.xml for each screen format.

You also have to update node-smile-server to get the following commit:
[#36] Adding 'createSessionFromTeacherApp()' to display the session id in the console