Several changes in Kruskal alg.
- Input object interface was changed to an STL compatible one.
- template parameters of class KruskalPairVec has been simplified.
- (the most of) the names meet the naming conventions.
- a lot of (but still not enough) documentation has been added.
- class KruskalMapVec has been commented out.

c

c        This is a simple example file to demonstrate the

c     DIMACS input file format for minimum-cost flow problems.

c 

c problem line :

p min 4 5

c

c node descriptor lines :

n 1 4

n 4 -4

c

c arc descriptor lines :

a 1 2 0 4 2

a 1 3 0 2 2

a 2 3 0 2 1

a 2 4 0 3 3

a 3 4 0 5 1