build warnings: prerequisites intended for maven-plugin projects

[vlukashov]

When running mvn jetty:run on a freshly cloned repo, I am getting the following warning in the build log:

[INFO] Scanning for projects...
[WARNING] The project org.vaadin.viktor:simpleapp:war:1.0-SNAPSHOT uses prerequisites which is only intended for maven-plugin projects but not for non maven-plugin projects. For such purposes you should use the maven-enforcer-plugin. See https://maven.apache.org/enforcer/enforcer-rules/requireMavenVersion.html

I would not want to see any such warnings in an example project that I download from vaadin.com/start.

[anasmi]

Still valid