Migrate BeakerXDoclet off from com.sun.javadoc.*

[LeeTZ]

These classes were deprecated long ago and are now removed in Java 13. We should get ready and migrate these classes. Some migration hints here: https://docs.oracle.com/javase/9/docs/api/jdk/javadoc/doclet/package-summary.html#migration

[jaroslawmalekcodete]

To do this we need to upgrade java