Major improvement in the cost scaling algorithm

- Add a new variant that use the partial augment-relabel method.
- Use this method instead of push-relabel by default.
- Use the "Early Termination" heuristic instead of "Price Refinement".

Using the new method and heuristic the algorithm proved to be
2-2.5 times faster on all input files.

p max 10 17

n 2 s

n 9 t

a 1 2 20

a 1 3 0

a 2 2 3

a 2 3 8

a 2 4 8

a 3 6 5

a 4 3 5

a 4 6 5

a 4 7 5

a 5 4 3

a 6 8 3

a 6 7 10

a 6 9 10

a 7 9 8

a 9 10 20

a 9 2 5

a 10 6 5