Remove JOGL and library specific AppSettings and the reflective code to instantiate non LWJGL3 desktop backends.

[riccardobl]

Originally jme used to support multiple opengl/al bindings on desktop, but nowadays we pretty much settled with LWJGL3.
We should deprecate all the LWJGL_ JOGL_ keys in AppSettings and add generic OPENGLXX OPENGLESXX to select opengl(es) versions (when possible).

We should also replace all this reflective code in JmeDesktopSystem

  @Override
    public JmeContext newContext(AppSettings settings, Type contextType) {
        initialize(settings);
        JmeContext ctx;
        if (settings.getRenderer() == null
                || settings.getRenderer().equals("NULL")
                || contextType == JmeContext.Type.Headless) {
            ctx = new NullContext();
            ctx.setSettings(settings);
        } else if (settings.getRenderer().startsWith("LWJGL") || settings.getRenderer().startsWith("ANGLE")) {
            ctx = newContextLwjgl(settings, contextType);
            ctx.setSettings(settings);
        } else if (settings.getRenderer().startsWith("JOGL")) {
            ctx = newContextJogl(settings, contextType);
            ctx.setSettings(settings);
        } else if (settings.getRenderer().startsWith("CUSTOM")) {
            ctx = newContextCustom(settings, contextType);
            ctx.setSettings(settings);
        } else {
            throw new UnsupportedOperationException(
                    "Unrecognizable renderer specified: "
                    + settings.getRenderer());
        }
        return ctx;
    }


    @Override
    public AudioRenderer newAudioRenderer(AppSettings settings) {
        initialize(settings);

        AL al;
        ALC alc;
        EFX efx;
        if (settings.getAudioRenderer().startsWith("LWJGL")) {
            al = newObject("com.jme3.audio.lwjgl.LwjglAL");
            alc = newObject("com.jme3.audio.lwjgl.LwjglALC");
            efx = newObject("com.jme3.audio.lwjgl.LwjglEFX");
        } else if (settings.getAudioRenderer().startsWith("JOAL")) {
            al = newObject("com.jme3.audio.joal.JoalAL");
            alc = newObject("com.jme3.audio.joal.JoalALC");
            efx = newObject("com.jme3.audio.joal.JoalEFX");
        } else {
            throw new UnsupportedOperationException(
                    "Unrecognizable audio renderer specified: "
                    + settings.getAudioRenderer());
        }

        if (al == null || alc == null || efx == null) {
            return null;
        }

        return new ALAudioRenderer(al, alc, efx);
    }

with known class paths eg. com.jme3.system.DesktopGL that the backend modules (such as jme3-lwjgl3) can implement.

This should probably be resolved after we get rid of the lwjgl2 backend.

Some non-breaking progress on this was made as part of #2776 to simplify android development