This is a big refactor and general cleanup of the land detector. The
main functional change is to share the hysteresis lib across all land
detectors.

Since the auto disarm hysteresis was implemented wrongly, it's now
replaced with the hysteresis library call.

The result from `!get_freefall_state()` was always true because
`get_freefall_state()` is already called before `get_landed_state()` is
called. Only if we're not in a freefall, we check if we are landed.

The hysteresis was not properly implemented in the land detector and is
therefore replaced by the library call, both for the freefall detector
and the land detector.

Sometimes, we only need a histeresis in one direction.

There have been two cases where a hysteresis function wasn't working
correctly. It is therefore a good idea to abstract the hysteresis
functionality into a library.

* make tests use px4 instead of mainapp

* commander_tests ALTCTL - not rotary requires altitude

- px4_getopt is threadsafe
- getopt does not do argument reordering (ms5611 start -T 5607 did not work)

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

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