Refactoring for integration with IoC frameworks like AutoFac, Unity etc

The idea is to be able to register an autofac container which can be used to resolve task orchestrations and activity instance objects.

In terms of the user model I was thinking that it should be similar to how Autofac integrates with Web API e.g:
http://blogs.msdn.com/b/roncain/archive/2012/07/16/dependency-injection-with-asp-net-web-api-and-autofac.aspx

Basically the dtfx exposes something like IDependencyResolver and then a separate package implements this for autofac and unit etc etc.