Always interpret closures as factories

[mnapoli]

When a factory is at the root of the definition array, it is automatically interpreted as a factory (DI\factory() is not necessary).

However it's not the case if the closure is in an array or an object parameter.

We could simplify the behavior and always consider a closure as a factory. If a user wants to really inject a closure, DI\value() is here for that. The behavior will at least be more consistent and simple.