[crrcsim] fix udp sending compatibility with OSX
[nps] fix number of actuator commands used

This makes it finally possible to have e.g. a hexarotor:
Six "commands" (one per motor) from motor_mixing sent to the FDM.
[ground_segment] sane error when launching settings without specifying aircraft
[ground_segment] python settingsapp: no default ac ids
[uart] fix name for parity value
ignore .idea dir from JetBrains IDEs
[boards] stm32f4_discovery: fix/switch LED 3 and 4

to match board doc and silkscreen
[conf][nps] same simple_quad JSBSim model for most quadrotors
[ahrs] gx3 minor fixes

closes #565
[stabilization] float_euler fixes so it actually compiles
[rotorcraft] quat_float: rename x_sum_err_eulers to x_sum_err
[telemetry] fix INS_Z
[fixedwing] add PERIODIC_SEND_AHRS_QUAT_INT
[fixedwing] remove sys_time include from autopilot.h
[test] update compare_ahrs
[modules] gps_ubx_ucenter: USB support

closes #569
[doc] minor descrption update for gps_ubx_ucenter
[dox] fix filename for baro_mpl3115
[boards] fix umarim BARO_ABS_ADS
[conf] remove non-functional FIRMWARE define

Defines don't work this way...
Was only used in gps_ubx_ucenter, replace it with GPS_UBX_UCENTER_SLOW_NAV_SOL flag
to set a lower NAV_SOL message rate (currently not set anywhere).
So you get full NAV_SOL messages rate for fixedwings as well
(just like before since the test for rotorcraft firmware was non-functional and always true).