feature: define tracing - log inputs and outputs

[aoancea]

This decorator is going to support the logging of inputs and outputs of every method from a class, thus, I define the following interface and its implementation:

public interface IFoo
{
    string Bar(string text);
}

public class Foo : IFoo
{
    public string Bar(string text)
    {
        return text;
    }
}

Given the above interface, I define the following decorator

public class Foo_IO_Decorator : IFoo
{
    private readonly IFoo decorated;

    public Foo_IO_Decorator(IFoo decorated)
    {
        this.decorated = decorated;
    }

    public string Bar(string text)
    {
        // TODO: provide a mechanics to log the input
        string result = decorated.Bar(text);
        // TODO: provide a mechanics to log the output

        return result;
    }
}

Note: For methods which don't accept any parameters or return void, input and respectively output logging will be NOT be performed.