Support negative costs and bounds in NetworkSimplex (#270)

* The interface is reworked to support negative costs and bounds.
- ProblemType and problemType() are renamed to
SupplyType and supplyType(), see also #234.
- ProblemType type is introduced similarly to the LP interface.
- 'bool run()' is replaced by 'ProblemType run()' to handle
unbounded problem instances, as well.
- Add INF public member constant similarly to the LP interface.
* Remove capacityMap() and boundMaps(), see also #266.
* Update the problem definition in the MCF module.
* Remove the usage of Circulation (and adaptors) for checking feasibility.
Check feasibility by examining the artifical arcs instead (after solving
the problem).
* Additional check for unbounded negative cycles found during the
algorithm (it is possible now, since negative costs are allowed).
* Fix in the constructor (the value types needn't be integer any more),
see also #254.
* Improve and extend the doc.
* Rework the test file and add test cases for negative costs and bounds.

 INCLUDE_DIRECTORIES(

   ${PROJECT_SOURCE_DIR}

   ${PROJECT_BINARY_DIR}

 )

 LINK_DIRECTORIES(${PROJECT_BINARY_DIR}/lemon)

 ADD_EXECUTABLE(lgf-gen lgf-gen.cc)

 TARGET_LINK_LIBRARIES(lgf-gen lemon)

 ADD_EXECUTABLE(dimacs-to-lgf dimacs-to-lgf.cc)

 TARGET_LINK_LIBRARIES(dimacs-to-lgf lemon)

 ADD_EXECUTABLE(dimacs-solver dimacs-solver.cc)

 TARGET_LINK_LIBRARIES(dimacs-solver lemon)

 INSTALL(

   TARGETS lgf-gen dimacs-to-lgf dimacs-solver

   RUNTIME DESTINATION bin

   COMPONENT bin

 )

 IF(NOT WIN32)

   INSTALL(

     PROGRAMS ${CMAKE_CURRENT_SOURCE_DIR}/lemon-0.x-to-1.x.sh

     DESTINATION bin

     COMPONENT bin)

 ENDIF(NOT WIN32)