Add ASP.NET Core SignalR integration package

[dotnetjunkie]

See: #232 (comment)

This package should do the following:

• Implement a SimpleInjectorHubActivator<T> class
• Add an extension method for registration of this class
• Add an extension method that allows auto-registration of Hub classes, similar to the RegisterMvcControllers of the ASP.NET Core MVC integration package. i.e. it should register Hub classes based on the selected lifestyle (ILifestyleSelectionBehavior) and should suppress the disposable transient components warning in case the Hub implementation does not override Dispose(bool).

Especially this last point is the main reason why we need an integration package. Integrating SignalR without an integration package would have been trivial in case Hub would not have implemented IDisposable (and it shouln't have).

[dotnetjunkie]

Won't fix.