Implement Minimum-cost flow Algorithm by the Boost Graph Library and Chinese Postman Problem for pgRouting

Minimum-cost flow problem is an extension of maximum flow problem with an added cost (per unit flow) for each edge. The Chinese Postman Problem (ChPP) in a directed graph or an undirected graph can be solved by Minimum-cost flow algorithm.
I am proposing to add Minimum-cost flow algorithm and directed ChPP algorithms to pgRouting during this GSoC period.