Add support for interfaces in generic methods

[rhodon-jargon]

This way, an expression in a generic method that references an interface member can be translated as long as the runtime generic argument is a concrete type. For example:

public static IQueryable<int> SelectComputedProperty<TConcrete>(this IQueryable<TConcrete> concretes)
    where TConcrete : InheritedModelTests.IBase
    => concretes.Select(x => x.ComputedProperty);

Here, when SelectComputedProperty is called like SelectComputedProperty<InheritedModelTests.Concrete> (where the argument can be implicit like in InheritedModelTests.cs), the correct implementation method can be found in Concrete.
However, when it is called like SelectComputedProperty<InheritedModelTests.IBase>, the concrete implementation is unknown and the method can't be translated.

I also changed overriding member logic (from #52) to use MethodInfo.GetBaseDefinition() instead of the name and signature of the method.

I changed some tests, because there were two duplicate tests in InheritedModelTests.cs. I assumed these modifications were the original intention.

Possible improvements:

• Additions to documentation
• Maybe some extra tests
• Helpful user feedback, like throwing an error when the generic argument is an interface (and thus can't be translated)

Thanks for creating and maintaining this package!

[koenbeuk]

Awesome! I'll review this tomorrow.