Add show QR-code in myaddress detail screen

src/bitmessagekivy/main.kv

@@ -246,6 +246,8 @@ MDNavigationLayout:
             id:id_draft
         AddressBook:
             id:id_addressbook
+        ShowQRCode:
+            id:id_showqrcode
 
     MDNavigationDrawer:
         id: nav_drawer

src/bitmessagekivy/screens_data.json

@@ -70,5 +70,10 @@
         "kv_string": "draft",
         "name_screen": "draft",
         "Import": "from pybitmessage.bitmessagekivy.baseclass.draft import Draft"
+    },
+    "Qrcode": {
+        "kv_string": "qrcode",
+        "Import": "from pybitmessage.bitmessagekivy.baseclass.qrcode import ShowQRCode"
     }
+  
 }