[modules] baro ets start delay
[modules] airspeed ets start delay
[stm32] F4: fix ppm input timer frequency for TIM2

- krooz: don't use TIM2 for PWM
- change to 6 ticks per usec to fit all frequencies
- on the F1 we assume to run at 72MHz for HCLK and both timer clocks
  TIM1 -> APB2 = HCLK = 72MHz
  TIM2 -> 2 * APB1 = 2 * 36MHz = 72MHz
- on the F4 we assume 2 * AHB clock:
  TIM1 -> 2 * APB2 = 168MHz
  TIM2 -> 2 * APB1 = 84MHz

closes #470
[electrical] don't try to use ADC_CHANNEL_CURRENT in SITL
[imu][aspirin_2_spi] clear naming for mag axes assignment
[krooz] add imu driver for KroozSD board from Sergei
[rotorcraft] fix MODE_STARTUP

- init nav, guidance and stabilization from autopilot_init
- after init of the above, set the autopilot_mode so it propagates to the guidance submodes.
- also call autopilot_init after the ahrs_init for ahrs_is_aligned check...
[spi] spi for stm32f4
[spi] update apogee and krooz board files for spi
Added check if autopilot_motors_on do determine if you want to switch to AP_MODE_FAILSAFE
Merge pull request #473 from flixr/rotorcraft_startup_mode

[rotorcraft] fix MODE_STARTUP
[ardrone2] Parrot GPS show sattelite information.

closes #474
[rotorcraft] motor_mixing: only lower throttle when hitting both min/max saturations

should be a minor improvement for issue #385, but not tested in real flight.
[modules] baro_amsys: usable for ins_alt_float with USE_BARO_AMSYS

- also clean up indentation

closes #476
[stm32][pwm] add PWM_SERVO_9
[boards] update krooz_sd, thx Sergei
[conf] update krooz_sd examples, thx Sergei
[conf] add krooz_sd fixedwing example, thx Sergei
[modules] ets baro/airspeed: cleanup and default delay of 0.2s

- airspeed_ets: use AIRSPEED_ETS_SYNC_SEND instead of SENSOR_SYNC_SEND
- baro_ets: use BARO_ETS_SYNC_SEND instead of BARO_ETS_TELEMETRY
Merge branch 'ets_start_delay'

* ets_start_delay:
  [modules] ets baro/airspeed: cleanup and default delay of 0.2s
  [modules] airspeed ets start delay
  [modules] baro ets start delay

closes #477