new ArithmeticalDSS (as a primitive representation) with main operators and accessors
 adding iterator services to arithmetical DSSs
cleaning and testing steps and shift vectors
adding update services (for extension)
Add forgotten methods in COBANaivePlane and COBAGenericNaivePlane.
adding update services (for retraction)
Add Chord naive plane recognition algorithm.
adding drawing services + aliases
cleaning
refactoring ArithmeticalDSSComputer
cleaning ArithmeticalDSS + adding contructors
using GreedySegmentation instead of the deprecated GreedyDecomposition
removing the deprecated GreedyDecomposition class
new example for arithmetical DSS computer
Merge branch 'PrimitivesArithmeticalDSS' into PrimitivesArithmeticalDSSDecomposition
Merge branch 'master' of github.com:DGtal-team/DGtal into FixCOBA

This is to check that the fusion is valid.
Updating documentation.
Changing names of plane recognition algorithms to ...NaivePlaneComputer. Fixing some doc.
Fix default parameter threshold in examples greedy-plane-segmentation*.
Add example for ChordNaivePlane.