FlightTaskManual: Yaw lock with deadzone and expo

More than a year ago I started the easy to use math::Functions to handle
the always used mathematical SISO functions to be tested and available.

I switched x, y and z stick input to the freesh programmed deadzone and
exponential functions from the library to unify and clarify their use.
I just realized yaw was left over because it lead to a drift problem in
certain new use cases.

Now I'm just adding the yaw stick to the already well working method.

src/lib/FlightTasks/tasks/FlightTaskManual.hpp

@@ -60,7 +60,7 @@ protected:
 
 	bool _sticks_data_required = true; /**< let inherited task-class define if it depends on stick data */
 	matrix::Vector<float, 4> _sticks; /**< unmodified manual stick inputs */
-	matrix::Vector3f _sticks_expo; /**< modified manual sticks using expo function*/
+	matrix::Vector<float, 4> _sticks_expo; /**< modified manual sticks using expo function*/
 
 	float stickDeadzone() const { return _stick_dz.get(); }
 
@@ -76,6 +76,8 @@ private:
 					(ParamFloat<px4::params::MPC_XY_MAN_EXPO>)
 					_xy_vel_man_expo, /**< ratio of exponential curve for stick input in xy direction */
 					(ParamFloat<px4::params::MPC_Z_MAN_EXPO>)
-					_z_vel_man_expo /**< ratio of exponential curve for stick input in z direction */
+					_z_vel_man_expo, /**< ratio of exponential curve for stick input in z direction */
+					(ParamFloat<px4::params::MPC_YAW_EXPO>)
+					_yaw_expo /**< ratio of exponential curve for stick input in yaw for modes except acro */
 				       )
 };