To now, each property hat an _invalidationLevel field that was evaluated by processors when the property had changed in order to determine what has to be done. However, since properties could also be owned by other classes, this design was semantically misleading.
Therefore, it was removed with this commit and replaced by the invalidation map of each processor. Now, this per-processor mapping of property -> invalidation level is managed by the processor itself. Furthermore, the invalidation level is no longer setup during property creation but during AbstractProcessor::addProperty(), which also makes much more sense.

ATTENTION: Due to these intrusive API changes, the code of all processors and other classes handling properties needs to be changed. As a reminder, the implementation of addProperty() also now takes a reference instead of a pointer, so that old code does no longer compile.

refs #542

removed obsolete scr_msk module. Code for Christian's IPCAI '13 submission on orientation-driven ultrasound compounding will be reimplemented from scratch at some point anyway.

Introduced manualsegmentation module with a HIGHLY EXPERIMENTAL processor and pipeline for manual segmentation of tissue layers. This code not really intended for use in other code but only to keep the somewhat extensive code for later reuse.

Added implementation for IEEE SciVis 14 submission on "Predicate-based Focus-and-Context Visualization for 3D Ultrasound" (Schulte zu Berge et al.) to advancedusvis module:
* Introducing AbstractPointPredicate base for point predicates and various derived classes
* Introducing PointPredicateHistogram, its corresponding PointPredicateHistogramProperty and the PointPredicateHistogramPropertyWidget
* Introducing PointPredicateEvaluator, PointPredicateRaycaster, PointPredicateVolumeExplorer and ScanlineDistributionComputation processors
* Added demo/reference pipeline implementations for the four data sets from the paper: Achilles tendon, shoulder and two carotid arteries

Removed ITK dependency from CmBatchGeneration pipeline and replaced Gaussian computation with GlGaussianFilter processor.

Module file parsing now supports new fields "ThisModApplicationSources", "ThisModApplicationHeaders", and "ThisModApplicationToBeMocced". These files will be added to the campvis-application package (instead of to the campvis-modules package) and thus for instance allow a module to declare property widgets in a non-intrusive way.

Little bug fix in glvesselnessfilter.frag shader.

* Introducing SliceExtractor::onEvent() to handle mouse events and generate point scribbles from it, which are then published using the s_scribblePainted signal
* Implemented SliceExtractor being able to render geometry in the slice space (with correct clipping)
* Implemented creating and handling of scribbles in VolumeExplorer in cooperation with the SliceExtractor. Therefore, mouse events are passed to the SliceExtractor, the VolumeExplorer takes care of assembling the scribbles into proper geometry, which is finally rendered by the SliceExtractor. The scribbling can be optionally turned on using the VolumeExplorer::p_enableSclibbling property.

* Added GCC pragma to ignore false-positive warning in ItkWatershedFilter

* Introduced tgt::Shader::IgnoreUniformLocationErrorGuard
* Fixed SimpleRaycaster::updateProperties() and OptimizedRaycaster::updateProperties() not calling base class' updateProperties()

* Updated ProcessorDecoratorGradient to support controllable LOD for gradient computation
* updated RaycastingProcessor to compute min/max depth values of entry/exit points and set as uniforms if needed by shader

* 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

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

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

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

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

Fixed GCC warnings in ItkImageFilter (false positive). Removed ItkImageFilterKernel, as they throw even more GCC warnings and meanwhile CAMPVis has the GlMorphologyFilter processor doing the same much faster and elegant.