Fixes in the heap concept to avoid warnings (#180)

Add citations to CycleCanceling (#180, #184)

Entirely rework cycle canceling algorithms (#180)

- Move the cycle canceling algorithms (CycleCanceling, CancelAndTighten)
into one class (CycleCanceling).
- Add a Method parameter to the run() function to be able to select
the used cycle canceling method.
- Use the new interface similarly to NetworkSimplex.
- Rework the implementations using an efficient internal structure
for handling the residual network.
This improvement made the codes much faster.
- Handle GEQ supply type (LEQ is not supported).
- Handle infinite upper bounds.
- Handle negative costs (for arcs of finite upper bound).
- Extend the documentation.

Port cycle canceling algorithms from SVN -r3524 (#180)

Add citations to the scaling MCF algorithms (#180, #184)
and improve the doc of their group.

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