Small doc improvements + unifications in MCF classes (#180)

Small implementation improvements in MCF algorithms (#180)

- Handle max() as infinite value (not only infinity()).
- Better GEQ handling in CapacityScaling.
- Skip the unnecessary saturating operations in the first phase in
CapacityScaling.
- Use vector<char> instead of vector<bool> and vector<int> if it is
possible and it proved to be usually faster.

More options for run() in scaling MCF algorithms (#180)

- Three methods can be selected and the scaling factor can be
given for CostScaling.
- The scaling factor can be given for CapacityScaling.