Ordering issue in VRPLIB files

[N-Wouda]

This:

EDGE_WEIGHT_SECTION
0     1544  1944  1931  1476
1726     0  1992  1427  1593
1965  1975     0  621   1090
2063  1433   647  0     818
1475  1594  1090  828   0
EDGE_WEIGHT_TYPE : EXPLICIT
EDGE_WEIGHT_FORMAT : FULL_MATRIX

has some of the specifications after the edge weight data. This does not currently work, because VRPLIB parses the EDGE_WEIGHT_SECTION the moment it encounters it and assumes all relevant specifications are known by that time. Clearly, here, they are not, and that causes an error. I don't think it should, but if it should, we should definitely clarify that we explicitly assume the specifications come first in the data file.

I ran into this when I was rewriting the GVRP instances yesterday.