Updated launch4j configuration, for new ClassiCubeSelfUpdater build.
Fixed UpdateTask errors not being logged.
Fixed regressions in UpdateTask, and fixed another edge case: if launcher is not started from its usual location, we need to take care to avoid repeated attempts to update it. We check if "launcher.jar.new" is up-to-date (instead of checking "launcher.jar"), and only download it if UpdateMode is not DISABLED.