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
+                }
+            }
         }
     }
 

src/qml/Base/HNumberAnimation.qml

@@ -1,10 +1,10 @@
 import QtQuick 2.12
 
 NumberAnimation {
-    property real factor: Math.max(overshoot / 1.75, 1.0)
+    property real factor: 1.0
     property real overshoot: 1.0
 
-    duration: theme.animationDuration * factor
-    easing.type: overshoot > 1 ? Easing.InOutBack : Easing.Linear
+    duration: theme.animationDuration * Math.max(overshoot / 1.7, 1.0) * factor
+    easing.type: overshoot > 1 ? Easing.OutBack : Easing.Linear
     easing.overshoot: overshoot
 }

src/qml/Base/HPage.qml

@@ -18,12 +18,13 @@ SwipeView {
         Math.min(theme.spacing * width / 400, theme.spacing)
 
     id: swipeView
-    currentIndex: 1
     clip: true
     interactive: sidePane.reduce
+    currentIndex: 1
 
     SidePane {
         implicitWidth: swipeView.width
+        animateWidth: false  // Without this, the SidePane gets auto-focused
         collapse: false
         reduce: false
         visible: swipeView.interactive