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/PageSetupWizardCredentials.qml

@@ -14,6 +14,11 @@ PageType {
 
     defaultActiveFocusItem: hostname.textField
 
+    Item {
+        id: focusItem
+        KeyNavigation.tab: backButton
+    }
+
     BackButtonType {
         id: backButton
 
@@ -21,6 +26,8 @@ PageType {
         anchors.left: parent.left
         anchors.right: parent.right
         anchors.topMargin: 20
+
+        KeyNavigation.tab: hostname.textField
     }
 
     FlickableType {
@@ -107,6 +114,8 @@ PageType {
 
                 text: qsTr("Continue")
 
+                Keys.onTabPressed: lastItemTabClicked(focusItem)
+
                 clickedFunc: function() {
                     forceActiveFocus()
                     if (!isCredentialsFilled()) {