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