Add documentation about configuring well-known actors

[craigfowler]

A quirk of the dependency injection, which may be leveraged, is that specifically-named parameters will resolve using a matching registration name.

For example:

[Test, Screenplay]
public void MyTest(Actor joe)
{
  // Implementation omitted
}

In this example, the resolver will first try to resolve the actor using the registration name "joe". If it finds no matching registration then it will use a nameless registration.

This can be leveraged in the setup logic to preconfigure the actor before passing it to the test logic.

A test should be constructed for this scenario to verify that it works like this.

[craigfowler]

The test should cover SpecFlow as well as NUnit.

[craigfowler]

Won't fix, this is not a good way of configuring actors.