Append Container to IServiceCollection

[dotnetjunkie]

Multiple integrations in ASP.NET Core now require the registration of generic activator instances. Those generic types need to be injected with the Container, but because of their generic nature, they need to be composed by MS.DI.

To make integration simpler, the Simple Injector ServiceCollection integration should, by default, append the Container to the IServiceCollection. This makes integration more straightforward, because now users don't have to register the Container themselves. It also makes the documentation more straightforward.

[dotnetjunkie]

feature-787 branch created.