This reverts commit 0c81a19decde6ddfe4ce87c34c762ea15fd3ab09.

But fix the two crucial problems:
- When to begin the ramp?
There's a calculation now for the velocity ramp initial value
such that the resulting thrust is zero at the beginning.
- When to end the ramp?
The ramp is applied to the upwards velocity constraint and it
just ramps from the initial value to the velocity constraint
which is applied during flight. Slower/going down is always possible.

Without always updating the takeoff state it will not get skipped when
the takeoff happened manually and when you switch from manual to position
mode the drone goes to idle and falls.

There are two local_position_setpoint in the position controller.
One describing the setpoint the task gives to the position controller
and a second one with the output of the position controller. I corrected
the wrong one during takeoff because the new takeoff thrust ramp runs after
the controller and not before.

In a deterministic way with clear states to go through.

The velocity ramp had problems with:
- different vehicle tunings resulted in the start value of the resulting
thrust ramp staring either higher and lower than zero thrust.
lower -> delay of beginning
higher -> small jump at beginning
- when a task set position and velocity at the same time during takeoff
(which AutoSmoothVel does) it resulted in a velocity setpoint
jump at the end of the ramp because the additional velocity
setpoint correction from the position controller was not considered.

The thrust ramp should now be very deterministic:
- always start at zero
- always end at the curreant thrust setpoint output
of the complete position controller

The initial idea of the flight task architecture was that
a task can freely set it's setpoints and doesn't have to
worry about takeoff and landing. It would just takeoff
when it's landed and there's a setpoint to go up and
land when it puts a setpoint that pushes into the ground.
With the takeoff logic there are some significant interface
problems depending on the way a task is implemented:
From the setpoint is not high enough to trigger to
an unexpected takeoff because of some estimator
fluctuation affecting the setpoint. It's easiest to solve this
by allowing the task to determine when a takeoff is triggered.
If no condition is implemented by default a task is not
allowing a takeoff  and cannot be used to get the vehicle
off the ground.

After boot the user is in manual mode and if he has an RC
but doesn't switch out the thrust gets set to the throttle stick
position. When he then starts a takeoff from tablet the thrust is still
high while arming and the land detector immediately sees a takeoff
skiping smooth takeoff from the position controller.

according to @dagar's review comment.

- start from a velocity setpoint pushing into the ground
to ramp from idle thrust up.
- start with a bit higher velocity setpoint threshold to make
sure the vehicle has a chance to really get off the ground.
- calculate ramp slope from initialization setpoint to the desired one
instead from zero to the desired. this ramps up quicker when you demand
a very small upwards velocity like the AutoLineSmoothVel and
ManualPositionSmoothVel tasks do at the beginning.
- don't stay in the takeoff ramp depending on the land detector, this
is unnecessary.

The comments and variable names were partly misleading.
I grouped all members, hopefully gave them more
understandable names and adjusted the comments.

There were two rather confusing function calls one to check
if smooth takeoff needs to be ran and one that updates it.
I combined them and documented the interface correctly
making the parameters non-reference const floats.

Co-Authored-By: Matthias Grob <maetugr@gmail.com>

Add jerk parameter for auto mode MPC_JERK_AUTO. Specify when a parameter is only used in a certain manual or auto mode

For now we need to ignore this warning which GCC 9 shows for the MAVLink
headers.

* VTOL trans: changed that now in transition for both MC and FW the corresponding (correct) attitude controller is running
* attitude setpoint for stabilized mode is generated by tailsitter.cpp
* reset yaw setpoint during transition to avoid big yaw errors after
transition back to hover
* VT_TYPE parameter: added "reboot required" metadata

To be able to still infer the direction of the thrust vector we
limit it to a minimal length even if MPC_THR_MIN is set to zero.

Note: This is a hotfix for certain specific applications.
The direction of the thrust vector in this corner case is very
likely to get into the tilt limit which is generally undesired.

A low gyro cutoff is needed for most medium/large size drones as the structural natural and blade-pass frequencies are low.
A higher value is still desirable for small platforms surch as racers
or well isolated autopilots and should be tuned by the user.
Specific values for config files are untouched.
The cutoff filter for the D term is disabled here as the required
cutoff frequency for the default D term of the rate controller is higher
than the gyro cutoff. In that case, enabling the D term cutoff would
just add some undesired phase lag to the derivative.

This fixes a potential dead-lock when 'uorb status' was used via MAVLink
shell.
The dead-lock chain is: DeviceMaster::lock() -> printf -> output to a pipe,
which blocks until a reader reads the data. In that case it's mavlink.
If mavlink makes a call that requires DeviceMaster::lock() (such as
orb_exists), it dead-locks.

This patch moves all printf's out of the locked state.

- when either terrain data was temporarily not valid (flying at high
distance to the ground) or the vehicle was not close to the ground
(_param_ekf2_gnd_max_hgt) the ekf switched to using the land detector
ground effect flag.

Signed-off-by: Roman <bapstroman@gmail.com>

- takeoff help is used for fixed wings, it increases the altitude setpoint
after a launch. A vtol does not need this as it's already sufficiently
high up in the air.

Signed-off-by: Roman <bapstroman@gmail.com>

This reverts commit 4a71984f.

The noise for airspeed is now applied on the Gazebo side and we can
remove this hack.

the condition to enter the rc mode switch evaluation was neglecting
the first connection of an RC when "no RC switch changed". this means
depending on the actual initialization values of _last_sp_man and the
desired mode preselected on the RC while connecting it would not get
evaluated.

pure refactor using De Morgan's law to make the condition more intuitive
since you think about when should I enter and not when should I skip