implemented SubproblemsExtractor
added inter-section interval getter for variables to ProblemConfiguration
added getter for LinearConstraints by variable list
improved (well, fixed) command line help for option 'branchSizeRatioThreshold'
changed nomenclature: Sub{solution,problem}[s] -> {Solution,Problem}[s], in favour of new Subproblem class
rewrote SubproblemsExtractor for new Subproblems data structure
implemented SubproblemsWriter
implemented sketch of SubproblemsSolver, hooked it into Sopnet pipeline creation