[Bug] AppCreationScripts and ReadMe need updating

[SergeyDubinets]

https://github.com/Azure-Samples/active-directory-xamarin-native-v2/tree/master/1-Basic

I see two distinct issues:

1. Configure1.ps is broken. It searches for clientID: "7d8cef0-4145-49b2-a91d-95c54051fa3f" wile source files use now "4a1aa1d5-c567-49d0-ad0b-cd957a47f842" as a result script doesn't do its work.

2. Change ba736f2 [Author: Jean-Marc Prieur [email protected] 2020-06-02 04:57:07]
   Added the use of WebAuthenticationBroker.GetCurrentApplicationCallbackUri().
   Now sample works with your clientID but when I substitute another clientID on UWP I get an error that callback URI is unrecognized.
   There is no surprise in this as on UWP we pass some different callback and APP registration doesn't know about it.
   Readme.md doesn't mention this and still shows old code https://github.com/Azure-Samples/active-directory-xamarin-native-v2/blob/master/1-Basic/README.md#about-the-code