This reverts commit be048ae2.

- remove custom xml view, use springboot builtin xml view
- remove oxm maven dependency
- remove json-simple maven dependency (seems not relevant anymore)
- update vetsXml test using xpath

- In the Jdbc implementation: pets belonging to a visit were not added.
- In the Jpa implementation: query variable was wrong.
- Test case: AbstractClinicServiceTests.shouldFindVisitsByPetId()

CallMonitoringAspect is not invoked when spring-data-jpa is used.  Spent
4 hours trying to understand why jmx bean wasn't showing message counts.
Use JPA or JDBC if you want call counts exposed via JMX / AOP

RSS is becoming outdated, JSon is a better example