Investigate treatment of JAR files

Java applications are usually distributed as JAR files. To benefit from cvmfs mechanics, JAR files should be cut on file or zip run boundaries. This only makes sense, however, if the java jar loader uses partial reads on the jar file.

Otherwise, we should document that the recommended way to deploy java applications in cvmfs is to extract the jar file and to start with java -cp $/cvmfs/path/to/jar $mainclass.