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.

 The authors of the 1.x series are

  * Balazs Dezso <deba@inf.elte.hu>

  * Alpar Juttner <alpar@cs.elte.hu>

  * Peter Kovacs <kpeter@inf.elte.hu>

  * Akos Ladanyi <ladanyi@tmit.bme.hu>

 For more details on the actual contribution, please visit the history

 of the main LEMON source repository: http://lemon.cs.elte.hu/hg/lemon

 Moreover, this version is heavily based on the 0.x series of

 LEMON. Here is the list of people who contributed to those versions.

  * Mihaly Barasz <klao@cs.elte.hu>

  * Johanna Becker <beckerjc@cs.elte.hu>

  * Attila Bernath <athos@cs.elte.hu>

  * Balazs Dezso <deba@inf.elte.hu>

  * Peter Hegyi <hegyi@tmit.bme.hu>

  * Alpar Juttner <alpar@cs.elte.hu>

  * Peter Kovacs <kpeter@inf.elte.hu>

  * Akos Ladanyi <ladanyi@tmit.bme.hu>

  * Marton Makai <marci@cs.elte.hu>

  * Jacint Szabo <jacint@cs.elte.hu>

 Again, please visit the history of the old LEMON repository for more

 details: http://lemon.cs.elte.hu/svn/lemon/trunk