[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
[electrical] don't try to use ADC_CHANNEL_CURRENT in SITL
[rotorcraft] add MODE_STARTUP to make flying without RC possible

- MODE_STARTUP defaults to AP_MODE_KILL (as before), but can be set to AP_MODE_NAV
- 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...
- Added check if autopilot_motors_on do determine if you want to switch to AP_MODE_FAILSAFE
[ardrone2] Parrot GPS show sattelite information.

closes #474
[imu][aspirin_2_spi] clear naming for mag axes assignment
fix google maps version download parsing

also set the default example version to 129
[imu] remove old aspirin2 driver
[imu] aspirin_v2.2: unselect baro at startup

- prevent floating CS line on the MS5611 baro connected via SPI
  so it also works if the baro is actually not read
- this requires to have the appropriate SPI_SLAVE defined in the board file
  which is the case for the lisa autopilots
[fix][fixedwing] init state interface _before_ sensors and ins

This had the very very nasty effect that the local coordinate system was not initialized
if NavSetGroundReferenceHere() was not called from the fliht plan,
(e.g. because not waitinf for GeoInit to finish).
[modules] silence some warnings in imu_chimu
[fix][lpc21] workaround for init of spi_slave_hs
20s timeout and max 2 retries when trying to update_google_version
[imu] aspirin_2_spi: default AHRS_PROPAGATE_FREQUENCY is 512

With DLPF_256HZ (value zero) the internal sampling rate is 8kHz and with a sample rate divider of 1
the output freq was actually 4kHz and not 500Hz. Since the data is polled from the mpu at PERIODIC_FREQUENCY
the AHRS_PROPAGATE_FREQUENCY (defaulting to PERIODIC_FREQUENCY) is also 512Hz for a default rotorcraft config.

Set the output freq to 2kHz now, AHRS_PROPAGATE_FREQUENCY stays at PERIODIC_FREQUENCY=512Hz so doesn't have to be
defined in the airframe file.

Also added defaults for PERIODIC_FREQUENCY of 60 and 120Hz:
- DLPF_42HZ
- output rate of 100Hz
In these cases add <define name="AHRS_PROPAGATE_FREQUENCY" value="100"/>
[mcu][i2c] fix/add i2c3 initialization
[release] v5.0.1 stable version
[sim] add launch and noground options to pprzsim-launch
[fixedwing] fix initialzation of trim commands, including yaw
fix to use ins_alt_dot with baro wen USE_BAROMETER is defined
[modules] baro_board: only call event handler if there is new data
[modules] fix warning in baro_board