Various improvements in NetworkSimplex.

- Faster variant of "Altering Candidate List" pivot rule using make_heap
instead of partial_sort.
- Doc improvements.
- Removing unecessary inline keywords.

@nodeset

label

0

1

2

3

4

5

6

@edgeset

        weight

0   3   1

0   4   1

1   5   1

5   2   1

6   2   1

0   1   1

2   1   1

3   4   1

4   5   1

5   6   1

@end