all: add id() helper to all exposed classes

include/eigenpy/angle-axis.hpp

include/eigenpy/decompositions/EigenSolver.hpp

include/eigenpy/decompositions/LDLT.hpp

include/eigenpy/decompositions/LLT.hpp

include/eigenpy/decompositions/PermutationMatrix.hpp

include/eigenpy/decompositions/SelfAdjointEigenSolver.hpp

include/eigenpy/decompositions/minres.hpp

include/eigenpy/decompositions/sparse/LDLT.hpp

include/eigenpy/decompositions/sparse/LLT.hpp

include/eigenpy/quaternion.hpp

include/eigenpy/solvers/BFGSPreconditioners.hpp

include/eigenpy/solvers/BasicPreconditioners.hpp

include/eigenpy/solvers/ConjugateGradient.hpp

include/eigenpy/solvers/LeastSquaresConjugateGradient.hpp

include/eigenpy/std-array.hpp

include/eigenpy/std-vector.hpp