Simplify startup and improve its animation

- Remove Python.loadingAccounts/willLoadAccounts
- Fix HPage SwipeView bug that caused its inner SidePane to steal focus

- Use overshoot for animation
- Get rid of sidepane flickering
- Set default HNumberAnimation easing.type to OutQuad, specify InOutQuad
  for HCheckBox

src/qml/Base/HCheckBox.qml

@@ -30,7 +30,12 @@ CheckBox {
 
             visible: scale > 0
             scale: box.checked ? 1 : 0
-            Behavior on scale { HNumberAnimation { overshoot: 4 } }
+            Behavior on scale {
+                HNumberAnimation {
+                    overshoot: 4
+                    easing.type: Easing.InOutBack
+                }
+            }
         }
     }