velocity setpoint generated from position error over velocity feedforward

PositionControl: remove takeoff logic

mc_pos_control: takeoff logic for flighttask

mc_pos_control: smooth takeoff throttle start at 0

FlightTaskAuto: add type that corresponds to triplet type

FligthTaskAuto: set all setpoints if invalid in xy

FlightTaskAuto: cast triplet type to WaypointType

FlightTaskAutoLine: class for px4 legacy auto

FlightTaskAutoLine: methods prototype

FlightTaskAuto: change sp to wp (=Waypoint)
add params

FlightTaskAutoLine: follow waypoints along line based on flight state

  Using the port name is platform dependent. It may give not
  provide the correct feedback. The port can be ttyS, or ftdi
  or CDC/ACM. While it is true that buadrate does not matter on
  CDC/ACM. It is better to give more information about what the
  code is doing before filtering by the port name.

Move MNT_MODE_IN / MOUNT_MODE_OUT logic block to rc.interface and move dataman, send_event, and load_mon startup just below uorb and tone_alarm startup in the rcS script.

This fixes automatic upload. Since ed95dced the NuttX string
is used for device detection, but Linux uses the bootloader's USB vendor
and product strings.
So the NuttX strings must match with the ones from the bootloader.

   The correct determination of Windowed mode is critical to
   maximise the speed on a USB based upload.

   This commit bases the detection of a Serial (FTDI) on the
   fact a CDC ACM port (USB) does not really have a baud rate.
   We bump the baud rate to 233% of the requested baud rate to
   see if the SYNC is acked. If it is Acked it must be a USB
   port and Windowed mode is turned off. This removes unnessary
   baud rate based delays from the proframing logic. If it is a
   real Serial port getSync will not get the ACK and Windowed
   mode is turned on.

When a gyro driver is stopped, the topic is unadvertised and
orb_group_count() returns a smaller count. This can have the effect, that
we poll on a certain gyro fd, but since _gyro.subscription_count is reduced
we never do the orb_copy for that fd.

This cannot happen when armed. And only someone playing with the shell
can trigger it (sensor failures do not have that effect).

This makes sure that poll() never returns immediately.
accel & mag are only updated to keep the code in sync.

Should some of these be of interest to someone, we should create a profile.

Copy/paste logic in rc.interface to group MIXER and MIXER_AUX logic, alphabetize hardware list in rc.interface, alphabetize set/unset lists in rcS, and add -p argument to pwm failsafe calls per issue #9775.