Merge: Tnitter: read the latest tnits on the go with the new Tnitter portable app!

Intro a portable client for Tnitter listing the more recent 16 tnits. It is more of a test and example on using `AsyncHttpRequest` to do both simple request to a REST server and implement push notifications using an open request. By design, this client does not support posting Tnits, this feature would require much more code and it may be simplified by future services in the lib.

To support the client the server has a few new REST interfaces. One to list the tnits and the other for push notifications.

This PR also fixes a few bugs on the Tnitter server: losing the session on posting and empty post being accepted by the server.

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Note for the reviewers: You may be better to read commits individually. There are 2 bigs commits, one extracts the database logic from the model module and the other introduces code generated by Jwrapper for the native layer of that Android ui implementation.

Pull-Request: #1834
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Romain Chanoir <romain.chanoir@viacesi.fr>