Improve code layout, add Doxygen comments.

pub/CMakeLists.txt.user

pub/lib/calc.cpp

pub/lib/calc.hpp

pub/lib/commands.cpp

pub/lib/commands.hpp

pub/lib/curve.cpp

pub/lib/curve.hpp

pub/lib/dualplot.cpp

pub/lib/dualplot.hpp

pub/lib/edif.hpp

pub/lib/expr.hpp

pub/lib/file_in.hpp

pub/lib/file_out.hpp

pub/lib/fit.hpp

pub/lib/geni.cpp

pub/lib/geni.hpp

pub/lib/node.cpp