* autodiff/cppad: fix eigen min check

* codegen/cppadcg: fix call to eigen min and max functions

* autodiff/cppad.hpp: add eigen::internal::pmin specialization

* codegn/cppadcg: eigen::internal::pmin/pmax specialization

* autodiff/cppad/minmax: create a file to deal with coeff wise min/max operation in eigen.
This file needs to be loaded before Eigen/Core is called, to load the correct environment for autodiff/codegen.
Otherwise, std::min/max is read by the compiler.

* autodiff/casadi: fix header

* traits.hpp: create traits file, which is independent from eigen

* codegen/cppadcg, autodiff/cppad.hpp: include minmax.hpp

* math/fwd: use traits.hpp instead of fwd.hpp. avoids loading eigen

* utils/static-if: use traits.hpp to avoid using eigen

* include pinocchio/fwd.hpp header
	modified:   src/multibody/joint/joint-free-flyer.hpp
	modified:   src/multibody/joint/joint-revolute-unbounded.hpp
	modified:   src/spatial/inertia.hpp

* add boost-mpl-container-limit header in codegen and autodiff files
	modified:   src/autodiff/cppad.hpp
	modified:   src/codegen/cppadcg.hpp

* add pinocchio/fwd.hpp header where missing

* add copyright license

* fwd.hpp: move enums to fwd.hpp

* [unittest/cppad-basic] add testing for cppad support for eigen min and max

* autodiff/cppad: fix inclusion order of minmax

* src, unittest: fix header inclusion order.

* cppad.hpp: add min/max computation in cppad. simplify implementation