adds additional file-based batchGenerator
some fixes to the weighted APSP implementation
reorganization of APSP metric (unweighted)

- adds separate computation method for R version
- changes returned values and comparisson
adds weight notion to metric naming conventions
reorganization of APSP metric (weighted)
adds name-only constructor to DistributionLong
refactors APSP metrics
fixes a bug in the InWeighted APSP implementation
fixes bug in ReadableFilesBatchGenerator (no suffix correctly set)