An experimental LPSolverWrapper class which uses glpk. For a short
demo, max flow problems are solved with it. This demo does not
demonstrates, but the main aims of this class are row and column
generation capabilities, i.e. to be a core for easily
implementable branch-and-cut a column generetion algorithms.

 p min 3 3

 n 3 s

 n 2 t

 a 3 1 20 20

 a 1 2 20 10

 a 1 2 20 0