Revert "Add a class for the construction of optimization problems"

src/CMakeLists.txt

src/ZMPRefTrajectoryGeneration/generator-vel-ref.cpp

src/ZMPRefTrajectoryGeneration/generator-vel-ref.hh

src/ZMPRefTrajectoryGeneration/mpc-trajectory-generation.cpp

src/ZMPRefTrajectoryGeneration/mpc-trajectory-generation.hh