[imu] use OrientationRep for body_to_imu
[settings] add settings to change BODY_TO_IMU
[imu] possibily to set imu_to_body to current roll/pitch and reset to airframe values
[imu] move settings handlers to c file
[settings] rename imu_to_body to body_to_imu.xml
[imu] imu_SetBodyToImuCurrent: only adjust by current roll/pitch

so you can use it if initial body_to_imu is not zero and also use it repeatedly
[imu] imu_to_body settings: combine set current and reset in one
[airborne][fixedwing] #756 Correct altitude setpoint offset during NavGlide
Merge pull request #785 from Drumettaz/master

[airborne][fixedwing] #756 Correct altitude setpoint offset during NavGl...
Merge pull request #783 from flixr/body_to_imu

[imu] body_to_imu: use generic orientation representation and expose it in settings to change during operation

You can now change the body_to_imu orientation via settings from the GCS, which should make experimentally "tuning" this for nice hover easier.
Also added setting "b2i curr roll/pitch" to set body_to_imu to current roll/pitch (on TRUE) and reset it to airframe file values on FALSE.
removed outdated lisa overo stuff
[imu] aspirin_2_spi: wait 1.5s before configuring mag

Seems that sometimes the mag is not correctly set to continuous measurement mode if it is configured immediately.
Delaying the configuration until the first single measurement was done seems to do the trick.

Delay configurable via ASPIRIN_2_MAG_STARTUP_DELAY

closes #779
update CHANGELOG
[math] add parenthesis to RMAT macros
[gcs] fix AC display when GCS section is defined but not AC_ICON
[video_sync] fix warnings
Merge branch 'master' of https://github.com/paparazzi/paparazzi into delflyDesperado