NSubstitute auto default values from fixture (fixes #297)

The solution is similar to what @dcastro did for AutoMoq on #302, but for NSubstitute.

There are a few differences, though:
It works with ref parameters
It won't setup void methods due to a limitation in NSubstitute that does not allow to override When..Do setups

Notes:
I had to late bind the NSubstitute methods because the signature of Returns and ReturnsForAnyArgs methods has changed a few times since 1.4.3 (had optional parameters added and return type changed). 
I added the classes that late binds the methods to the AutoFixture kernel as I though it might be helpful for someone else.

```LateBindingStaticMethodQuery```: Selects public static methods that has the same parameters of another method, ignoring optional parameters and return type.
```LateBoundMethod```: Decorates another method invoking it supplying missing optional parameters.
```GenericMethod```: Encapsulates a generic method, inferring the type parameters bases on invocation arguments.


As @mrinaldi points out, this is a limitation of Castle.Core. IIRC, it also doesn't support overriding `Equals`. Effectively, it can't override virtual methods defined on System.Object.

AFAIR, Moq also uses Castle.Core, so it has the same limitation.