Simplify findNumberOfNoFathers method.
Correct findNumberOfNoFathers method, refactor dump methods.
Refactor and simplify method PeronsByBirthdate.
Change javadoc to properly describe methods and parameters.
Simplify method findAllFathers.
Refactor and simplify findAllPersonWithSameName method.
Refactor displayPersons method, add toString method to Person class.
Add entity manager method.