Correlations algorithms refactoring
The whole histogram code has been redone, and the code has been simplified. The three-point vertex-edge-vertex correlation has been scrapped, since it's not frequently used, and would make compilation even more expensive. This also adds some missing files to the generation routine.
src/graph/correlations/graph_correlations_combined_corr_imp1.cc → src/graph/correlations/graph_correlations_bind.cc