qml: implement toggle for android SECURE_FLAG and add marker to wizard pages

that should be secured.

electrum/gui/qml/components/wizard/WCConfirmSeed.qml

@@ -8,6 +8,8 @@ import ".."
 import "../controls"
 
 WizardComponent {
+    securePage: true
+
     valid: false
 
     function checkValid() {

electrum/gui/qml/components/wizard/WCCreateSeed.qml

@@ -7,6 +7,8 @@ import org.electrum 1.0
 import "../controls"
 
 WizardComponent {
+    securePage: true
+
     valid: seedtext.text != ''
 
     function apply() {

electrum/gui/qml/components/wizard/WCHaveMasterKey.qml

@@ -9,6 +9,7 @@ import "../controls"
 
 WizardComponent {
     id: root
+    securePage: true
 
     valid: false
 

electrum/gui/qml/components/wizard/WCHaveSeed.qml

@@ -9,6 +9,7 @@ import "../controls"
 
 WizardComponent {
     id: root
+    securePage: true
 
     valid: false
 

electrum/gui/qml/components/wizard/WCImport.qml

@@ -8,6 +8,7 @@ import "../controls"
 
 WizardComponent {
     id: root
+    securePage: true
 
     valid: false
 

electrum/gui/qml/components/wizard/Wizard.qml

@@ -2,6 +2,8 @@ import QtQuick 2.6
 import QtQuick.Layouts 1.0
 import QtQuick.Controls 2.1
 
+import org.electrum 1.0
+
 import "../controls"
 
 ElDialog {
@@ -141,6 +143,11 @@ ElDialog {
                 _setWizardData({})
             }
 
+            Binding {
+                target: AppController
+                property: 'secureWindow'
+                value: pages.contentChildren[pages.currentIndex].securePage
+            }
         }
 
         ColumnLayout {

electrum/gui/qml/components/wizard/WizardComponent.qml

@@ -11,6 +11,7 @@ Pane {
     property bool valid
     property bool last: false
     property string title: ''
+    property bool securePage: false
 
     leftPadding: constants.paddingXLarge
     rightPadding: constants.paddingXLarge