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/PageSettingsConnection.qml

@@ -11,8 +11,15 @@ import "../Config"
 PageType {
     id: root
 
+    defaultActiveFocusItem: focusItem
+
     property bool isAppSplitTinnelingEnabled: Qt.platform.os === "windows" || Qt.platform.os === "android"
 
+    Item {
+        id: focusItem
+        KeyNavigation.tab: backButton
+    }
+
     BackButtonType {
         id: backButton
 
@@ -20,6 +27,8 @@ PageType {
         anchors.left: parent.left
         anchors.right: parent.right
         anchors.topMargin: 20
+
+        KeyNavigation.tab: amneziaDnsSwitch
     }
 
     FlickableType {
@@ -44,6 +53,7 @@ PageType {
             }
 
             SwitcherType {
+                id: amneziaDnsSwitch
                 Layout.fillWidth: true
                 Layout.margins: 16
 
@@ -56,11 +66,14 @@ PageType {
                         SettingsController.toggleAmneziaDns(checked)
                     }
                 }
+
+                KeyNavigation.tab: dnsServersButton.rightButton
             }
 
             DividerType {}
 
             LabelWithButtonType {
+                id: dnsServersButton
                 Layout.fillWidth: true
 
                 text: qsTr("DNS servers")
@@ -70,11 +83,14 @@ PageType {
                 clickedFunction: function() {
                     PageController.goToPage(PageEnum.PageSettingsDns)
                 }
+
+                KeyNavigation.tab: splitTunnelingButton.rightButton
             }
 
             DividerType {}
 
             LabelWithButtonType {
+                id: splitTunnelingButton
                 Layout.fillWidth: true
 
                 text: qsTr("Site-based split tunneling")
@@ -84,6 +100,10 @@ PageType {
                 clickedFunction: function() {
                     PageController.goToPage(PageEnum.PageSettingsSplitTunneling)
                 }
+
+                Keys.onTabPressed: splitTunnelingButton2.visible ?
+                                       splitTunnelingButton2.forceActiveFocus() :
+                                       lastItemTabClicked()
             }
 
             DividerType {
@@ -91,6 +111,7 @@ PageType {
             }
 
             LabelWithButtonType {
+                id: splitTunnelingButton2
                 visible: root.isAppSplitTinnelingEnabled
 
                 Layout.fillWidth: true
@@ -102,6 +123,8 @@ PageType {
                 clickedFunction: function() {
                     PageController.goToPage(PageEnum.PageSettingsAppSplitTunneling)
                 }
+
+                Keys.onTabPressed: lastItemTabClicked()
             }
 
             DividerType {