delete Isabelle distribution archive after use;
documentation for "isabelle build_docker";
proper latex setup;
updated docker setup: lib32stdc++6 is no longer required for polyml-5.8, libfontconfig1 is required for headless jdk-11;
proper option (amending cc0b3e177b49);
updated for release;
updated to jdk-8u152, which is for x86_64 only;
build_docker is regular tool (non-admin); --HG-- rename : src/Pure/Admin/build_docker.scala => src/Pure/Tools/build_docker.scala