Implements #224 to use discontinuity mask

applications/reconstruct/src/ilw/ilw.cpp

applications/reconstruct/src/main.cpp

components/operators/CMakeLists.txt

components/operators/include/ftl/operators/mask.hpp

components/operators/include/ftl/operators/operator.hpp

components/operators/src/colours.cpp

components/operators/src/filling.cpp

components/operators/src/mask.cpp

components/operators/src/mask.cu

components/operators/src/mask_cuda.hpp

components/operators/src/normals.cpp

components/operators/src/operator.cpp

components/operators/src/segmentation.cpp

components/operators/src/smoothing.cpp