* Added optional picking information to GeometryData API
* GeometryRenderer processor renders the picking information into a separate texture if present
* geometrydata.h contains a stub for a possible rewrite of the API (more flexible buffer layout)

Made calls to ImageData::tryPerformConversion() mutually exclusive to avoid concurrent conversions to the same target data type.

Particle visualization

See merge request !95

Updated VectorFieldDemo pipeline to allow the user to choose between arrow- and particle visualization.

* Introducing ParticleFlowRenderer processor implementing a particle simulation using OpenGL transform feedback
* Added tgt::Shader::selectSubroutine()
* Added tgt::VertexArrayObject::getId()

Core updates

Various updates to the base library, cherry-picked from the biopsy-workflow-gui branch. Most notably:

* new AbstractJob instance taking C++11 functionals in the constructor
* new QtJobProcessor singleton for executing jobs in the Qt GUI thread
* new StatusProperty and StatusPropertyWidget to display status information as color+text
* ButtonProperty forwards clicks to its shared properties
* s_changed signal of properties is only fired if the value actually has changed
* MatrixProcessor fix for endless loops occuring when a formula uses a matrix that is computed by that same formula and that is put into the data container
* various accessors to internals of MainWindow and AbstractPipeline

See merge request !93

* Updated CMake scripts to work with new CMake 3 and TBB 4.3

core API change: properties don't emit s_changed signal if setValue() is called with the current value

* new QtJobProcessor singleton: used to execute jobs in the Qt thread
* CampvisApplication now has a map to obtain the window for a pipeline

* AbstractPipeline offers getter for the canvas to execute jobs in the pipeline's OpenGL context
* PropertyCollectionWidget adds a spacer element at the end to prevent element stretching when there is too much free space
* job.h offers new CallFunctionObjectJob to create jobs on the fly using lambda functions (the respective makeJob and makeJobOnHeap are inlined to prevent linker errors)

* Introducing visual regression testing framework
* Added PipelineResultImageTest case to run pipelines and write their rendering results to PNGs.
* Updated DevilImageWriter, added property to make writing depth images optional.

1. edited test-campvis::main to generate xml regardless of environment var. 2. check is the result image null. 3. open and edit the gtest output xml with results from python test

Registered testing thread and OpenGL context with OpenGLJobProcessor.

Cleaned up DevilImageReader to be working with all kinds of input images and being completely OpenGL free.

* Updated DevilImageWriter, added property to make writing depth images optional.

Fixed GenericImageReader referencing DevilImageReader even if the corresponding module was not present.

* AbstractImageReader is now again an AbstractProcessor, so that we can get rid of the dynamic_casts in GenericImageReader
* DevilImageReader is no longer a VisualizationProcessor but gets the OpenGL context through OpenGLJobProcessor::ScopedSynchronousGlJobExecution
* Fixed alglib's CMakeLists.txt

3d mi segment flat rebased

See merge request !89

campvis-test does not use OpenGLJobProcessor and only initializes it halfway. However, some CAMPVis functionality relies on that. Therefore, I introduced a hack/workaround to set the OpenGL thread manually if you need to.

Furthermore, added exit(EXIT_FAILURE) to recursive assertions to avoid possible endless assertion loops in campvis-test (and thus amok running jobs in Jenkins).