- arm without mission on by default

because there is no sense to have different angle scalings into different directions
it would lead to unintuitive piloting experience
acceleration is directly coupled to the tilt angle regardless of possible assymetric multicopter vehicles

land_detector: fix sanity condition that we have ground contact when we are landed to include the hysteresis flag
because the condition was looking for the instantaneous flag and during the hysteresis time the state did not change anymore

land_detector: treat altitude mode like position mode with vertical checks but without horizontal checks
because in altitude mode we have a baro available and can therefore check vertical movement
we can not check horizontal movement but I consider the checks for landing still pretty safe
unlike in manual mode we are not allowed to disarm before land detection in altitude mode

For example on px4cannode-v1_default.

This will avoid file system corruptions in cases where px4_shutdown_request
is used. However it will not help obviously when the battery is pulled
directly.

px4_board_pwr has become obsolete with the addition of board_shutdown

To get the new API definitions

  This adds the board power button notification registration
  and shutdown API points.

   Defined types and interface to support a notification call back
   on power button events.

Previously load stats were stored outside of the printloop, but
with the refactoring to save memory state was reset and used in
the first loop before the actual load calculations were valid.

Fixed by moving the summary info to the bottom of the top printout
after everything is computed. Also restructured the callback to
not depend on a line counter and fixed astyle glitches.

vmount is now added to the startup script, however, it will only start
if the param MNT_MODE_IN is set to anything but -1.

To reduce latency of the output update when mode is set to auto.