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.

 /* Define to 1 if you have long long */

 #undef HAVE_LONG_LONG

 /* Define to 1 if you have any LP solver. */

 #undef HAVE_LP

 /* Define to 1 if you have any MIP solver. */

 #undef HAVE_MIP

 /* Define to 1 if you have CPLEX. */

 #undef HAVE_CPLEX

 /* Define to 1 if you have GLPK. */

 #undef HAVE_GLPK

 /* Define to 1 if you have SOPLEX */

 #undef HAVE_SOPLEX

 /* Define to 1 if you have CLP */

 #undef HAVE_CLP

 /* Define to 1 if you have CBC */

 #undef HAVE_CBC