Renamed MessageListActivity to MainActivity

(it is the main activity, after all)

app/src/main/java/ch/dissem/apps/abit/SubscriptionDetailActivity.java

@@ -28,7 +28,7 @@ import android.view.MenuItem;
  * An activity representing a single Subscription detail screen. This
  * activity is only used on handset devices. On tablet-size devices,
  * item details are presented side-by-side with a list of items
- * in a {@link MessageListActivity}.
+ * in a {@link MainActivity}.
  * <p/>
  * This activity is mostly just a 'shell' activity containing nothing
  * more than a {@link SubscriptionDetailFragment}.
@@ -79,7 +79,7 @@ public class SubscriptionDetailActivity extends AppCompatActivity {
             //
             // http://developer.android.com/design/patterns/navigation.html#up-vs-back
             //
-            NavUtils.navigateUpTo(this, new Intent(this, MessageListActivity.class));
+            NavUtils.navigateUpTo(this, new Intent(this, MainActivity.class));
             return true;
         }
         return super.onOptionsItemSelected(item);