Decouple maven installation from Jenkins by using the reference applications maven build wrapper

[RobertNorthard]

The reference application (spring-petclinic) has a maven build wrapper. This enables the application to be built using mvn wrapper. E.g. ./mvnw clean install.

In my opinion, we should make use of this build wrapper because;

• It decouples the Maven installation from Jenkins.
• It helps ensure the build server is building/testing the application the same way as the developers.
• Maven version stored in version control alongside the application code.
• Easier to maintain different maven profiles/versions per application.

See #39 for example.