* Review the [dogfood ruleset](https://github.com/pmd/pmd/blob/master/pmd-core/src/main/resources/rulesets/internal/dogfood.xml). * Move the ruleset into the [build-tools](https://github.com/pmd/build-tools) subproject, so that we can use it properly in the maven-pmd-plugin executions. * Fix current issues / decide about priority * Enable dogfood ruleset, so that no new problems are introduced in future.