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
I tried to minimize the changes I was making to the other repos, so I kept MVC and SignalR's and just made them internal.  EF had some default logic already so Arthur was going to clean that up.  I deleted them in Identity/Hosting/Options since I know those repos well.