Now the profile safer includes the PMD plugin to check for errors or bad practices,
the configuration to fail the build is set to priority 2, so only highly critical
errors stop the build, the warnings (priority 3+) are send to target/pmd.xml report wich
should also be fixed.
This includes also a new profile called checker wich compiles the project using
the Checker Framework with some annotation processors activated, particulary the
NullnessChecker. Checker Framework only works on JDK 8.