Fr/45904 fix javadoc with jdk17
This fixes javadoc warnings shown in backoffice repo when running with JDK17 (ea9 build).
This those fixes run is clean again.
Testing on top: no problems in javadoc with JDK11 and those changes. Also checking that passing -Dfooter (with that parameter being removed) does not fail (as that is done during release)
Try (with jdk11 default): https://builds.openbravo.com/view/try/job/try-init/663/