Change IOptions<> to IOptionsSnapshot<>

[VahidN]

reloadOnChange parameter on the AddJsonFile method has no effect on the strongly typed configuration IOptions<> and only IConfigurationRoot is automatically updated whenever the underlying appsettings.json file changes. In ASP.NET Core 1.1.0 IOptionsSnapshot<> has the same behavior.
More info
ASP.NET Core Identity uses IOptions<> everywhere. so it would ne nice to replace IOptions<> with IOptionsSnapshot<> in this framework.

[RehanSaeed]

What is the point of IOptions<>? I fully expected the reason for it's existence being the reloading ability. Why was IOptionsSnapshot<> created instead and what use is IOptions<> anymore? Why not just register the options type directly?

[blowdart]

Dupe of aspnet/Options#163