[settings] fix GCS settings page when only one mode in a process

This solves the case where a process as only one mode by removing the
corresponding setting (since there is nothing to change) and by removing
the complete telemetry page if no more process.
The case without modes in a process fails at code generation since at
least one mode is required.

fix #553
[conf] remove obsolete RC_CLIMB_COEF and RC_CLIMB_DEAD_BAND
[rotorcraft][guidance_h] GUIDANCE_H_USE_SPEED_REF defaults to TRUE

This also allows to give velocity commands via RC in GUIDANCE_H_MODE_HOVER.
[fix] fix mpl3115 driver and apogee baro_board
[fix] if no baro and no kalman, get vz from gps
[state interface] fix stateCalcHorizontalSpeedNorm_i
[navigation] Rotorcraft compute distance to home