Add ToNewWindow and ToNewWindowAsTab methods to Go

[YevgeniyShunevych]

Add methods to Go and AtataNavigator classes:

public static T ToNewWindow<T>(T pageObject = null, string url = null, bool temporarily = false)
    where T : PageObject<T>;

public static T ToNewWindowAsTab<T>(T pageObject = null, string url = null, bool temporarily = false)
    where T : PageObject<T>;

Usage

Go.To<GoTo1Page>();

Go.ToNewWindow<GoTo2Page>()
    .PageUri.AbsolutePath.Should.EndWith("/goto2");

Go.ToPreviousWindow<GoTo1Page>()
    .PageUri.AbsolutePath.Should.EndWith("/goto1");