Multi-Tab Support

[tal-sarid]

Add support for adding additional explorers inside the app

[Alex4SSB]

ShellWindow > OnItemClick

var item = args.ClickedItem as HamburgerMenuGlyphItem;
            int index = MenuItems.IndexOf(item);
            ExplorerIndex = index.ToString();
            if (index == MenuItems.Count - 1)
                ExplorersAmount(MenuItems.Count + 1);

            NavigateTo(item.TargetPageType);

[Alex4SSB]

For now, multi window is supported.