Add IsLocal extention metod for Request
Check isLocal via Uri.IsLoopback

To do this we need to have proper request url string with protocol and host name. In order to do set HostName for testing i have added HostName field to IBrowserContextValue
Check isLocal using Uri.TryCreate. It is possible in case we have only absolute url.
Merge pull request #1451 from Adalyat/featIsLocal

Add IsLocal extention metod for Request