Added tab navigation functional. (#721)

- Added tab navigation functional.
- In basic types added parentFlickable property, which will help to ensure, that the item is visible within flickable parent during tab navigation.
- Added focus state for some basic types.
- In PageType qml file added lastItemTabClicked function, which will help to focus tab bar buttons when the last tab on the current page clicked.
- Added Focus for back button for all pages and drawers.
- Added scroll on tab for Servers ListView on PageHome.

client/ui/qml/Pages2/PageSetupWizardStart.qml

@@ -15,6 +15,8 @@ PageType {
 
     property bool isControlsDisabled: false
 
+    defaultActiveFocusItem: focusItem
+
     Connections {
         target: PageController
 
@@ -136,7 +138,13 @@ PageType {
                       qsTr(" Helps you access blocked content without revealing your privacy, even to VPN providers.")
             }
 
+            Item {
+                id: focusItem
+                KeyNavigation.tab: startButton
+            }
+
             BasicButtonType {
+                id: startButton
                 Layout.fillWidth: true
                 Layout.topMargin: 32
                 Layout.leftMargin: 16
@@ -147,9 +155,12 @@ PageType {
                 clickedFunc: function() {
                     connectionTypeSelection.open()
                 }
+
+                KeyNavigation.tab: startButton2
             }
 
             BasicButtonType {
+                id: startButton2
                 Layout.fillWidth: true
                 Layout.topMargin: 8
                 Layout.leftMargin: 16
@@ -167,11 +178,18 @@ PageType {
                 clickedFunc: function() {
                     Qt.openUrlExternally(qsTr("https://amnezia.org/instructions/0_starter-guide"))
                 }
+
+                Keys.onTabPressed: lastItemTabClicked(focusItem)
             }
         }
     }
 
     ConnectionTypeSelectionDrawer {
         id: connectionTypeSelection
+
+        onClosed: {
+            PageController.forceTabBarActiveFocus()
+            root.defaultActiveFocusItem.forceActiveFocus()
+        }
     }
 }