Bump libs to latest versions, improve /owners POST,PUT, add tests

- Updated pom.xml dependent libs to latest versions
- Added minimum code coverage rules in pom.xml
- Added petclinic-ermodel.png and added ref in readme.md
- /owners POST: update to ensure no id is given in request body
- /owners PUT: update to ensure bodyId (if given) matches pathId
- Add bad request tests to /owners POST,PUT
- Improve test coverage