refactor cartesian_tasks.py

[ichumuh]

• CartesianOrientation
• CartesianPosition
• CartesianPositionStraight
• CartesianPositionVelocityLimit
• CartesianRotationVelocityLimit
• CartesianVelocityLimit

[jehanzeb95]

ich nehme die erste vier Klassen, Marvin nimmt die letzte vier Klassen (JustinTorsoLimitCart brauchen wir nicht)

[ichumuh]

in CartesianOrientation and Position you only have to fix the absolute/relative part

[ichumuh]

        position_variables = r_P_c.free_variables()
        velocity_variables = [p.dof.variables.velocity for p in position_variables]
        r_P_c_dot = cas.Expression(r_T_c.to_position()).total_derivative(
            position_variables, velocity_variables
        )