TSP Problem Mask

[koalamitice]

Problem Mask to enter TSP problems.
We could use GML as input format here, but using the TSPLIB-95 TSP format would be better because it is well known.
--> TSPLIB format is preferred
Examples can be found here: http://comopt.ifi.uni-heidelberg.de/software/TSPLIB95/tsp/
(file names with "tour" are solutions, you can ignore them)

TSP solvers will be added by Lucas later, so we just need to problem mask at the moment (without a working solver)

[koalamitice]

@Elscrux can we add this to #51 ?