Improvements in MinCostFlow and MinCostMaxFlow.

Main changes:
- MinCostMaxFlow also provides dual solution.
- Change the name of private members to start with "_".
- Change the name of function parameters not to start with "_".
- Remove unnecessary documentation for private members.
- Doc improvements.

 #!/bin/bash

 echo '#include<'$1'>' >seedeps_tmp.cc

 gcc -MM -I. -I.. -I../.. $2 seedeps_tmp.cc|tr ':' ' '|tr '\' ' '|tr ' ' '\n'|

 egrep -v '^$'|egrep -v '.o$'|egrep -v '.cc$'|grep -v '^'$1'$'|sort

 rm seedeps_tmp.cc