Some test classes have been refactorized for a more consistent use of
the OwnersDataset class and for a simpler test implementation.

The REST layer has been added but with incomplete tests. Students will
have to complete the tests.

This commit includes an important refactorization regarding tests. Test
classes and datasets have been moved from the "service" project to a new
"tests" project. This way, any project can include this "tests" project
as a dependency in order to have access to these common testing
resources.

This commit adds the OwnerService and PetService EJBs to the
implementation. This commit also includes the tests for this EJBs with
two different Wildfly profiles: a H2 profile and a MySQL profile.

The "administrator" entity has been added to represent the
administrators of the application.