Cleanup GLContext special entries: getOffscreenContextPixelDataType(), getOffscreenContextReadBuffer(), .. ; Add GLFBODrawable API entries for multi buffering (no impl. yet); GLJPanel 1st simplification using offscreen drawable

- Cleanup GLContext special entries: getOffscreenContextPixelDataType(), getOffscreenContextReadBuffer(), .. ;
  - add: getDefaultReadBuffer() (-> exposed via GLBase as well)
  - add: isGLOrientationFlippedVertical()
  - add: getDefaultPixelDataType()
  - removed impl: getOffscreenContextPixelDataType()
  - removed impl: getOffscreenContextReadBuffer()
  - removed impl: offscreenImageNeedsVerticalFlip()

- Add GLFBODrawable API entries for multi buffering (no impl. yet);
  - TODO: Add implementation code in GLFBODrawableImpl

- GLJPanel 1st simplification using FBO
  - Use above new GL/GLContext entries
  - Fix: getNativeSurface() and getHandle()
  - TODO:
    - Remove distinction of 'pbuffer' and 'software',
    - Use GLDrawableFactory.createOffscreenDrawable(..)
    - Use GL for FBO swapping
GLArrayData/ImmModeSink: Remove implicit dependency on ShaderState - allow operating w/o it; ShaderState: Remove notion of GL context attachment, use pass-through or object association; GLArrayData/GLUniformData: Add basic GLSL location methods

- GLArrayData/GLUniformData: Add basic GLSL location methods
  - GLArrayData
    - add: setLocation(..) for attribute location/index retrieval (post link) and binding (pre link)
  - GLUniformData
    - add: setLocation(..) for attribute location/index retrieval (post link)

- GLArrayData/ImmModeSink: Remove implicit dependency on ShaderState - allow operating w/o it
  - GLArrayData
    - add: 'public void associate(Object obj, boolean enable)', allows setting ShaderState usage

- ShaderState: Remove notion of GL context attachment, use pass-through or object association
  - ownsAttribute(..) associates the attribute w/ ShaderState
  - removed GL context ShaderState attachment

Tested:
 - ImmModeSink w/ GLSL/ES2 w/ and w/o ShaderState
 - GLArrayData* w/ and w/o ShaderState
Fix/Complete commit b8a8fc24a3afb0cb06a31504bdea1a98b8f00ef4 - Adding missing GLU code
GLJPanel: Impl. is GLProfile agnostic; Use GLDrawableFactory.createOffscreenDrawable(..) for common OffscreenBackend (dropping pbuffer/software); Flip FBO w/ GLSL texture renderer.

- Implementation is GLProfile agnostic
  - Shall work on ES2, GL2, .. etc

- Use GLDrawableFactory.createOffscreenDrawable(..) for common OffscreenBackend (dropping pbuffer/software)
  - Leave offscreen selection to common factory code, favoring FBO

- Flip FBO w/ GLSL texture renderer
  - Faster on low CPU machines
  - Enabled if GL2ES2 and FBO offscreen
MacOSXCGLContext: Use new setLocation(gl, shader-program); Minor edits..
Bug642: Add test case for Swing JSplit Pane w/ GLCanvas and GLJPanel
test script
Cleanup atomic JARs; Removed Debug/Trace pipelines of common profiles

GLU:
  jogl-glu.jar <- jogl-glutess.jar, jogl-glumipmap.jar and
                  javax/media/opengl/glu/*
                  javax/media/opengl/glu/gl2es1/*
                  jogamp/opengl/glu/* jogamp/opengl/glu/error/*

  jogl-glu-gldesktop.jar stays.

CORE (jogl.core.jar):
  + com/jogamp/opengl/util/*
  + jogamp/opengl/util/*
  + com/jogamp/opengl/util/glsl/*
  + jogamp/opengl/util/glsl/*

DEBUG/TRACE: Removed Debug/Trace pipelines of common profiles (won't work anyways)
  - [Debug|Trace]GL2ES1
  - [Debug|Trace]GL2ES2
  - [Debug|Trace]GL2GL3