Refactor registrations to allow common usage patter

[sebastienros]

Instead of having this code:

var builder = new ContainerBuilder();

AutofacRegistration.Populate(
  builder,
  TestServices.DefaultServices(),
  fallbackProvider);

We would then have

var builder = new ContainerBuilder();

builder.Populate(
  TestServices.DefaultServices(),
  fallbackProvider);

[davidfowl]

Why isn't this closed and put in a milestone?