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.

 INCLUDE_DIRECTORIES(

   ${PROJECT_SOURCE_DIR}

   ${PROJECT_BINARY_DIR}

 )

 LINK_DIRECTORIES(

   ${PROJECT_BINARY_DIR}/lemon

 )

 SET(DEMOS

   arg_parser_demo

   graph_to_eps_demo

   lgf_demo

 )

 FOREACH(DEMO_NAME ${DEMOS})

   ADD_EXECUTABLE(${DEMO_NAME} ${DEMO_NAME}.cc)

   TARGET_LINK_LIBRARIES(${DEMO_NAME} lemon)

 ENDFOREACH()