Changes

• Issue #169: update to Checkstyle 8.25
• infra: update release.sh to do be more exact
• infra: add openjdk12 build
• infra: upgrade travis to do install
• infra: activate auto deployments in release.sh
• infra: udpate in release.sh to add 'mvn package' as it does web site generation

Please read the Checkstyle release notes for details on recent and potentially breaking changes in Checkstyle. Checkstyle configuration files potentially need to be adapted to this version.