* Split up ProcessorDecoratorShading in ProcessorDecoratorShading inheriting from ProcessorDecoratorGradient
* Introducing GlGradientVolumeGenerator processor in preprocessing module

removed getElementXD() and getElementXDNormalized() from core GLSL headers since the same functionality is directly provided by GLSL with texture() and texelFetch() in a much cleaner way.

 * use texture and textureOffset instead of clumsy getElement3DNormalized
 * introducing Sobel filtered gradients

* Updated DepthDarkening to use GlReduction to compute min/max depth

 * Added a stripped version of NLOPT sources as external library, so that the registration module can be built right away.
 * Some minor improvements in CMake files

* Introducing NloptRegistration pipeline performing the optimization
* SimilarityMeasure only computes the similarity and difference image

 * added computation of difference image to SimilarityMeasure
 * fixed possible out of bounds access in datacontainerinspectorwidget.cpp
 * added assertions to ImageRepresentationGL constructor

* OpenGl based reduction in core tools
* SimilarityMeasure processor stub

* Fixed pointer inconsistencies in ScopedTypedData and ScopedRepresentation

Conflicts:
	application/gui/datacontainerinspectorcanvas.cpp

+ some minor beautifications/fixes

Fixed tgt::FramebufferObject to work with Intel GPUs (for some reason, the Intel OpenGL driver fails generating and binding FBOs when using the core (non-EXT) GL functions).

+ Using passthrough.vert and geometryrenderer.frag instead of the meshGeometryRenderer.vert and meshgeometryrenderer.frag
+ adding comments for the destroy function of GeometryTextureInfo and why to use it.
+ Change the depth buffer size changing part of Paint() function in datacontainerinspectorcanvas checking part.
+ Delete the commented codes which are not necessary.
+ Fix the opening braces and removing the redundant parts and only for debugging parts.
+ DVRVis and volumerendererdemo default file is revereted to the original locations.
+ Revert the shaders to the original ones.
+ StartMouseDrag and EndMouseDrag functions of the trackball are replaced with mousePress and mouseRelease.

- Delete the meshGeometryRenderer.vert and meshgeometryrenderer.frag.

Merge branch 'OpenGL3-core-refactoring' of /mnt/bigone/git/repositories/berge/campvis into development

fixed CMake error introduced in e1551c26: CAMPVIS_HAS_MODULE_XYZ was no longer defined by CMake

Cleaned up and slightly revised GeometryData API. Cleared the way for non-value semantics. Introducing GeometryDataFactory, a collection of static methods to create standard geometric primitives.

When a new floating MDI window was created, its position was tracked
from the very beginning. This caused the window's initial move event,
generated by the show() method, to be handled by the undocking
mechanism.

This event might contain outdated position information that, in certain
cases, could trigger immediate re-docking of the floating window,
setting its pointer to 0. If this happened, then the remaining code that
configured the floating window would dereference the null pointer and
crash the application.

To fix the error, connect the floating window's signals only after it
has been fully configured. This way its initial move events are ignored.

work on Issue #88: cleaned up VertexArrayObject interface. It's now simpler and more straight-forward.

* Adapted shaders to new texture formats