fix qrcode

- Bigger qrcode
- Let the library choose qr version
- Lower the error correction level
- Keep the aspect ratio

Change-Id: I79bd49d2011b47f45f006741290feac199728749
Tuleap: #499
diff --git a/callwidget.h b/callwidget.h
index 085a2ae..f766ea9 100644
--- a/callwidget.h
+++ b/callwidget.h
@@ -111,7 +111,7 @@
     QMenu* shareMenu_;
 
     constexpr static int animDuration_ = 200; //msecs
-    constexpr static int qrSize_ = 100;
+    constexpr static int qrSize_ = 200;
 
 private:
     void findRingAccount();