additionals to use amsys sensors to measure airspeed
[math] fix ecef_of_[ned|enu]_i
[modules] remove unused baro_x_updated vars
[math] buf fix on geodetic function
[rotorcraft] add MODE_STARTUP to make flying without RC possible

Based on Freek van Tienen's commit, thx.
closes #467 for now
[lpc21] print error if trying to use SPI0 with HAL
[boards][krooz_sd] fix PPM Capture/Compare InterruptEnable define
[stm32] include stm32/flash.h instead of f1/4 variants
[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
Merge remote-tracking branch 'upstream/master'