BufferUtils.c and CallbackUtil.c have been modified to not include the
generated header file. This is because `javac` is choosing to ignore
those files for generation of headers for unknown reasons.
- Remove applet
- Remove webstart
- Refactor all generation to the `target` folder
- Remove eclipse-update
- Update java version in `.tool-versions`
- Update `.gitignore`
- Remove unused `res` folder
- Only macOS builds work currently
- TODO: finish the aforementioned changes to all other targets
- `build.sh` runs in headless mode to avoid the focus stealing and
performance issues on macOS