renamming
Add image extractor functor 3D -> 3D from ref points
merging with the master, solving small conflicts
renaming in ***DSSIterator.cpp
renaming in testDSLSubsegment
clean assert
Board3DTo2d + Viewer3D
merge and solve conflicts
Revert "clean assert"

This reverts commit 11fdfb5dccf91aca3d65a3c63cd0bebd5726acf7.
rewrote assert verify is now fatal_error
renamed verify to fatal_error
doc
added TCompare template param.

TCompare apply to the compare template param of std::set.
Update Object.ih. Add DigitalTopologyTraits. Improve speed of isSimple test.
another merge
Fixing domain problem in returned objects (class Object). Induce changes in digital sets (domains are now hold via counted pointers. Induce changes in Alias and ConstAlias and hence many fixes.
Update doc and concept accordingly. Update DigitalSetFromMap.
Add image (18,6) for thinning example.
Add OPENMP for homotopcThinning3D.
Merge branch 'master' of github.com:DGtal-team/DGtal into FixCOBA