mvp: Introducing Model View Presenter pattern

libringclient is a new module where we will put avery non Android code.
MVP must not depend on Android.

app now depends on that module. It should improve reusability.

Change-Id: I20c7d7adeed43212a21e5e617e6d2b6054db8a40
Tuleap: #1217
diff --git a/ring-android/settings.gradle b/ring-android/settings.gradle
index e7b4def..2c39028 100644
--- a/ring-android/settings.gradle
+++ b/ring-android/settings.gradle
@@ -1 +1 @@
-include ':app'
+include ':app', ':libringclient'