[ahrs] remove AHRS_UPDATE_FW_ESTIMATOR and ins_x_neutrals
[conf] remove ins_neutrals settings from example and test conf
[modules] hackhd: remove ins neutral
[control] add a pitch trim to replace the ins_pitch_neutral
[stm32] fix adc

very hack-ish fix for when using multiple ADs, e.g. AD1 and AD2
Before this "fix" e.g. AD1_1 and AD2_1 had the same value (0).

Can probably be done more nicely...
[mcu_periph] NB_ADC only needed for lpc21
Update README.md

Added gitter.im badge.
Merge pull request #816 from paparazzi/rm_ins_neutrals

remove AHRS_UPDATE_FW_ESTIMATOR and ins_x_neutrals
Merge pull request #822 from paparazzi/stm32_fix_adc

[stm32] fix adc

very hack-ish fix for when using multiple ADs, e.g. AD1 and AD2
Before this "fix" e.g. AD1_1 and AD2_1 had the same value (0).