Add filter to threshold an image

Conflicts:
	src-plugins/itkFilters/CMakeLists.txt
	src-plugins/itkFilters/itkFiltersPlugin.cpp
	src-plugins/itkFilters/itkFiltersToolBox.cpp
	src-plugins/itkFilters/itkFiltersToolBox.h
[SIZE_THRESH] A bit of clean
[DAVD] Add removal of small components before creating the meshes