Add functional and integration tests for Petclinic

Add 2 set of JBehave tests:
- [DMG-385] Web service tests validating Petclinic XML response - to be
  used as functional tests.
- [DMG-367] Selenium tests against Petclinic UI - integration tests.

The tests use GD JBehave Framework - see spring-petclinic-test/README.md
for details.