Major improvements in NetworkSimplex.

Main changes:
- Use -potenital[] instead of potential[] to conform to the usual
terminology.
- Use function parameter instead of #define commands to select pivot rule.
- Use much faster implementation for the candidate list pivot rule.
It is about 5-20 times faster now.
- Add a new pivot rule called "Limited Search" that is a modified
version of "Block Search". It is about 25 percent faster on rather
sparse graphs.
- By default "Limited Search" is used for sparse graphs and
"Block Search" is used otherwise. This combined method is the most
efficient on every input class.
- 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.
- Many 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