Debian: Change debian files from stretch (Jetty 9.2, Tomcat 8, Java 8) to buster (Jetty 9.4, Tomcat 9, Java 11)
Add debian-alt/stretch files
Update debian-alt/precise, trusty, xenial, bionic, disco to include
 the changes from buster, not stretch
Remove debian-alt/buster, unstable files
Doc updates