I'm wondering if we shouldn't just drop everything below this point and put a cleaned up version in a new java::jre definition ? There are at least 2 problems here:
 * we should use update-java-alternatives, as the JDK is mush more than /usr/bin/java and /usr/bin/javac. This currently can create a quite inconsistent JDK installation
 * As we're moving from a class to a definition, we'll have a conflict if several java::jdk instances are claiming to be the "default" java on the system.