Redesign the maximum flow algorithms

Redesigned interface
Preflow changed to use elevator
Edmonds-Karp does not use the ResGraphAdaptor
Goldberg-Tarjan algorithm (Preflow with Dynamic Trees)
Dinitz-Sleator-Tarjan (Blocking flow with Dynamic Tree)

c LEMON max flow problem

p max 7 9

n 1 s

n 7 t

a 1 2 3

a 1 3 2

a 1 4 1

a 2 5 3

a 3 5 2

a 3 7 5

a 3 6 3

a 4 6 1

a 5 7 2

a 6 7 4