GetDefaultServices -> AddSignalR

- Switch to TryAdd
- Removed SignalRServiceCollection since it broke chaining (its not a
IServiceCollection??) and only had Configure overload which is the same
as ConfigureSignalR on IServiceCollection
Not sure what you mean exactly, I added an AddSignalR to IServiceCollection but kept the GetDefaultServices as internal and just used the IEnumerable overload of TryAdd, since it was a smaller change that way.  

Looking at the tests again, you should be able to remove the AddOptions/AddDataProtection now that they are added by AddSignalR