Contravariant type search doesn't consider decorators for more general variants

[LordZoltan]

Expanding again on the shapes examples in the contravariance documentation, if we reimplement the RectangleComparer as a decorator and register it thus:

container.RegisterDecorator<RectangleComparerDecorator, IComparer<Rectangle>>();

We would expect both the following two assertions to hold:

Assert.IsType<RectangleComparerDecorator>(container.Resolve<IComparer<Rectangle>>());
Assert.IsType<RectangleComparerDecorator>(container.Resolve<IComparer<Square>>()); //fails

Unfortunately, the second fails because the contravariant search for IComparer<Square> doesn't pick up the decorator. It's clearly blind to anything other than a traditional registration.

See this test in the examples project:

Rezolver/test/Rezolver.Tests.Examples/ContravarianceExamples.cs

Lines 123 to 124 in d6d23f0

	[Fact]
	public void EmptyDecoratorShouldInjectContravariantBase()

It currently passes because it does partly demonstrate that contravariant decorators do almost work - but the crucial lines within it are commented out:

Rezolver/test/Rezolver.Tests.Examples/ContravarianceExamples.cs

Lines 141 to 142 in d6d23f0

	// BUG #54: this should also work:
	//Assert.IsType<RectangleComparerDecorator>(container.Resolve<IComparer<Square>>());

[LordZoltan]

This is actually related to #72