Added exercises for JShell and some resources for further practise after the session
Added exercises for JShell and some resources for further practise after the session

AdoptOpenJDK/jdk9-jigsaw,neomatrix369/jdk9-jigsaw,neomatrix369/jdk9-jigsaw,AdoptOpenJDK/jdk9-jigsaw,AdoptOpenJDK/jdk9-jigsaw,neomatrix369/jdk9-jigsaw