Even for well calibrated RC sticks 5% stick movement is a too small margin for the end user that might not land because of this.
15% is still clearly restricting the stick far down.

Rattitude: set default threshold for multicopter rattitude mode to 0.8 which enables it right away when selecting it

Switch assignment: added manual and stabilized switch for a default stabilized switch scheme, let FW go into Acro

* Fix several valgrind identified mem leaks

* Added callgrind target.

* px4_posix_tasks use nullptr

We need to protect access to the param_values array. This is dynamically
allocated and resized (utarray_reserve() calls realloc). If some thread
was iterating the array while another was resizing the array, the first one
would iterate on a freed array, thus accessing invalid memory.

On NuttX this could lead to hardfaults in rare conditions.

Unfortunately we need to initialize the semaphore on startup, by calling
sem_init(). This adds a param_init() method called by every board/config
that uses the params (at least I think I've found all of them)