Entirely rework CostScaling (#180)

- Use the new interface similarly to NetworkSimplex.
- Rework the implementation using an efficient internal structure
for handling the residual network. This improvement made the
code much faster.
- Handle GEQ supply type (LEQ is not supported).
- Handle infinite upper bounds.
- Handle negative costs (for arcs of finite upper bound).
- Traits class + named parameter for the LargeCost type used in
internal computations.
- Extend the documentation.

EXTRA_DIST += \

	scripts/bib2dox.py \

	scripts/bootstrap.sh \

	scripts/chg-len.py \

	scripts/mk-release.sh \

	scripts/unify-sources.sh \

	scripts/valgrind-wrapper.sh