React to Options changes

FYI the file is spelled wrong: SignalRServiceColletion
I'm not sure option 2 and 3 would work today, since SignalRServiceCollection is ironically not an IServiceCollection. This is something we should probably look into changing.

Regarding option 3: Would the IConfiguration be used to replace only the services registered by SignalR or all services already in the IServiceCollection? Or would it not even be used to replace services? This replacement is what is being done today by passing the IConfiguration into GetDefaultServices which obviously only affects SignalR services.

I assume that if it did replace services, it would only affect SignalR services, since it would be an extension method on SignalRServiceCollection. However, it might be more convenient to do the service replacement from config for all frameworks in one go.

Either way, while it might be relatively simple to pull options from IConfiguration fluently, right now it would be tricky to implement service replacement that way. IServiceCollection does not currently provide a way to replace items and IServiceDescriptor only provides getters for its properties.

I think we would wind up confusing customers if we have `services.AddSignalR(config)` do one thing and have `services.AddSignalR().Configure(config)` do something else.