Refactoring for integration with IoC frameworks like AutoFac, Unity etc #2

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.