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.

==================================================================

LEMON - a Library of Efficient Models and Optimization in Networks

==================================================================

LEMON is an open source library written in C++. It provides

easy-to-use implementations of common data structures and algorithms

in the area of optimization and helps implementing new ones. The main

focus is on graphs and graph algorithms, thus it is especially

suitable for solving design and optimization problems of

telecommunication networks. To achieve wide usability its data

structures and algorithms provide generic interfaces.

Contents

========

LICENSE

   Copying, distribution and modification conditions and terms.

INSTALL

   General building and installation instructions.

lemon/

   Source code of LEMON library.

doc/

   Documentation of LEMON. The starting page is doc/html/index.html.

demo/

   Some example programs to make you easier to get familiar with LEMON.

test/

   Programs to check the integrity and correctness of LEMON.

tools/

   Various utilities related to LEMON.