[radio_control] spektrum for nps/sim

Ocaml sim always uses the radio.xml file and sends ppm values in usec.
So for the time beeing you need to use the spektrum.xml radio file for the sim target if you really want to use the RC in the simple OCaml sim.

closes #503
[conf] update examples using spektrum for sim
Merge pull request #851 from paparazzi/spektrum_sim

[radio_control] spektrum for nps/sim

OCaml sim always uses the radio.xml file and sends ppm values in usec.
So for the time beeing you need to use the spektrum.xml radio file for the sim target if you really want to use the RC in the simple OCaml sim.

closes #503
[generators] add type bool for gen_settings
[rotorcraft] only go to HOME mode if in NAV

then you don't have this "failsafe" in manual modes anymore,
but it will prevent issues like #850