Add MySqlPersonDao and support classes

I want to demonstrate how to test the liskov substitution principle. In
order to do that I have to have a base class and a derived class from
the base class.

I created the PersonDao class as the base class, and MySqlPersonDao as
the derived class. In reality, I should have created the test class
first, since TDD demands it. However, my POC will not do anything
production; so, who cares if I follow strictly follow TDD