GetCryptoProviderForSha256 gives NullReferenceException when running locally

Hello,

I am having the same issue described at https://github.com/Azure/Azure-Functions/issues/683 where `Microsoft.IdentityModel.Clients.ActiveDirectory.CryptographyHelper.GetCryptoProviderForSha256(RSACryptoServiceProvider rsaProvider)` throws a null reference exception when running a v1 runtime project launched from within Visual Studio.

The issue said to open a new issue to obtain information on how to fix this

The issue links to [this commit](https://github.com/Azure/azure-functions-host/commit/7addbeeb687a43a25acb2535c180b0f3ea512964) as a fix to change the httpRuntime targetFrameworkVersion but I don't know how to do this on a function that is run locally.

Thanks.