Expose GraphicsDebug on AppSettings

[MeFisto94]

So someone was trying to debug why his shaders look odd under a different openGL Version and I remembered there was a way to make jme output non critical warnings/faults/driver messages, basically every call to glError.

This is hidden behind GraphicsDebug (

jmonkeyengine/jme3-lwjgl/src/main/java/com/jme3/system/lwjgl/LwjglContext.java

Line 111 in d57c362

if (settings.getBoolean("GraphicsDebug") || settings.getRenderer().equals(AppSettings.LWJGL_OPENGL3)) {

).

There should be a setGraphicsDebugMode(true) on AppSettings, the feature is next to undocumented.