Many doc improvements for Circulation (#175)

- More precise doc for members.
- Several doc fixes.
- Add doc for public types.
- Better formulations.
- Add useful notes to the problem description.
- Use supply instead of excess in the doc.
- Hide the doc of the traits class parameter.
- Use \tparam for template parameters.

prefix=@prefix@

exec_prefix=@exec_prefix@

libdir=@libdir@

includedir=@includedir@

Name: @PACKAGE_NAME@

Description: Library of Efficient Models and Optimization in Networks

Version: @PACKAGE_VERSION@

Libs: -L${libdir} -lemon

Cflags: -I${includedir}