[All] Remove useless namespace path pininvdyn::

include/pininvdyn/contacts/contact-6d.hpp

include/pininvdyn/contacts/contact-base.hpp

include/pininvdyn/inverse-dynamics-formulation-acc-force.hpp

include/pininvdyn/inverse-dynamics-formulation-base.hpp

include/pininvdyn/math/utils.hpp

include/pininvdyn/robot-wrapper.hpp

include/pininvdyn/solvers/eiquadprog_rt.hpp

include/pininvdyn/solvers/solver-HQP-base.h

include/pininvdyn/solvers/solver-HQP-eiquadprog-fast.h

include/pininvdyn/solvers/solver-HQP-eiquadprog-rt.h

include/pininvdyn/solvers/solver-HQP-eiquadprog-rt.hpp

include/pininvdyn/solvers/solver-HQP-eiquadprog.hpp

include/pininvdyn/tasks/task-actuation.hpp

include/pininvdyn/tasks/task-base.hpp

include/pininvdyn/tasks/task-com-equality.hpp

include/pininvdyn/tasks/task-contact-force.hpp

include/pininvdyn/tasks/task-joint-posture.hpp

include/pininvdyn/tasks/task-motion.hpp

include/pininvdyn/tasks/task-se3-equality.hpp

include/pininvdyn/trajectories/trajectory-base.hpp