* GlGaussianFilter performs a Gaussian blur
* GlIntensityQuantizer quantizes image intensities into bins using a transfer function
* GlSignalToNoiseRatioFilter computes a very simple variance-based SnR value
* GlVesselnessFilter computes a Frangi-similar vesselness measure

Refactor Propertywidget Registration

* Fixed RTTI type inference in PropertyWidgetFactory::createWidget()

Implemented a real PropertyWidgetFactory where property widgets can register themselves together with the property type they wrap around. Registration is implemented using CRTP do allow automatic registration across DLL boundaries during static initialization time.
This commit replaces the long list of if-else in PropertyWidgetFactory with a much more generic approach.

* GeometryRenderer supports textured rendering
* GeometryRenderer and RenderTargetCompositor support alpha blending of (semi-)transparent surfaces
* Updated GeometryRendererDemo to show a demo implementation of the new features

* Introducing virtual GeometryData::hasTextureCoordinates()
* Introducing virtual GeometryData::applyTransformationToVertices()

Implemented normalizing conversion between different GenericImageRepresentationLocal<BASETYPE, NUMCHANNELS> representations as proof-of-concept. This conversion might not always yield expected results since it remaps the entire input data type range to the entire output data type range. While this is reasonable for downcasts (narrowing conversions) a histogram stretch for widening conversions is probably not expected or wanted by the caller.

A more flexible and elaborate conversion as well as automatic conversion from ITK and OpenGL representations will need a redesign of the conversion interface since we're fighting with severe cyclic include dependency problems here. The future design should provide the possibility to externally register conversion functions for new data types that are not necessarily known in the core package (i.e. ITK representations).

refs #474

Removed AbstractImage::getSubImage() interface since it's implementation in all subclasses is far from trivial and therefore was not done thoroughly. Since the functionality was not used anywhere so far, it was removed to avoid unexperienced users trying to use it and getting confused if it does not work as intended.
Could be reimplemented in extra processors for special cases.

closes #339

Fixed GeometryTransferFunctionEditors trying to initialize their OpenGL contexts from non OpenGL thread.

ITK Filter to include Thresholding

hacked into vector field branch before MICCAI - now ready for merging

Fixed MSVC builds not supporting shared linking against module sublibs (as campvis-modules is built statically). As workaround RandomWalksLib and nlopt-stripped are forced to be build static.

refs #385

Module Status

Updated and refactored CAMPVis module build system: CAMPVis module .cmake files now define two additional Variables:
* ThisModStatus defines the status of the module and should be one of STABLE, TESTING or EXPERIMENTAL
* ThisModExternalDependencies defines, whether this module has further external dependencies that are not shipped

The main CAMPVis build system now ships a new enumeration option CAMPVIS_DEFAULT_ENABLED_MODULES, which can be one of "NONE" "STABLE_NO_DEPENDENCIES" "STABLE_WITH_EXTERNAL_DEPENDENCIES" "TESTING" and "ALL". The INCLUDE_MODULE() function in the build scripts will evaluate the modules' status information and enable every module that matches the specified value.

ATTENTION: Due to these changes in the build system, the modules' cmake files should put their setup block into an IF(ModuleEnabled) block, since the file is also parsed, when the module is not enabled (in order to gather the status information).

closes #385

VectorField

VectorField renderer, pipepline, and nice sampledata.

Small refactorings related to issue #367

TGT and campvis-core used to manually define flags that instructed their
code to export DLL symbols. However, CMake has a property called
DEFINE_SYMBOL that can automatically define export flags when necessary.
Refactor the CMakeLists of TGT and campvis-core to make use of it.

References #367

CAMPVis used a custom option, CAMPVIS_SHARED_LIBS, to determine whether
shared or static libraries should be built. This option partially
duplicated the functionality of one of CMake's standard flags,
BUILD_SHARED_LIBS. The two could get out of sync, and because CMake only
consults BUILD_SHARED_LIBS when deciding how to build a library target,
it was possible to get inconsistent and broken build configurations.

To prevent that, add BUILD_SHARED_LIBS as an option to CAMPVis' main
CMakeLists and replace all references to CAMPVIS_SHARED_LIBS with
BUILD_SHARED_LIBS. This makes BUILD_SHARED_LIBS the only flag that
controls whether shared or static libraries are built.

References #367

Data Inspector Jenkins Fix

I have fixed all of the Jenkin's errors but there was another thing in source/modules/randomwalk/processors/confidencemapgenerator.cpp which should be fixed but I think the variable in Line 207 may not be used anywhere but it is added to some object in create function. The only thing which I can do is to omit the confidenceMap pointer definition.

Fixed TrackballNavigationEventListener setting the window ratio of its CameraProperty being directly overwritten due to concurrent access.

Fix Cppcheck Issues