This is required in order for JOGL to work.
It's ugly, I know. But right now, there doesn't seem to exist a better
solution. Let's hope it doesn't break anytime soon...

We need to set Multi-Release to true so that log4j can determine the
correct class names. Otherwise, the app wouldn't work when running as a
jar (and not inside an IDE).

With this approach, we don't have to maintain two separate build scripts
and keep both up-to-date. Also, you can invoke Gradle now directly
instead of calling the old build scripts. Those are only kept for
compatibility reasons.

There may be some issues left to make the app fully work. However, this
should pretty much cover the additional building steps required.

Instead of parsing the arguments and replacing the paths to the log files
with absolute paths, we'll just keep the current working directory. We then
refer to the Jar file through the already existing DIR variable.

This also supports setting the Dock icon on macOS if the application is
running inside of a bundled application.

And on top of that, the script should now be compatible with other
POSIX-compatible shells (not just bash).

Otherwise, we'd try to copy the jar file before it was created.

Until now, RoboViz would not start without a config file being present.
Now, we'll just use the default hardcoded configuration values in that
case. When attempting to save the configuration using the built-in
configuration editor, RoboViz will ask if a new configuration file
should be initialized (if none is present so far).