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)
adding update services (for retraction)
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
convex-and-concave-parts example fixed
greedy-decomposition example fixed
tutorials fixed
refactoring of extend* isExtendable* where the backward case is deduced from the forward case
refactoring of retract* where the backward case is deduced from the forward case
checking validity in external functions
DSS creation methods are put in a separate static class (factory)