Merge pull request #163 from DTFUHF/master

Adds AK8975 (compass inside MPU-9150) support, changes mag init structure to copy accel init.
Merge pull request #164 from DTFUHF/master

fix comment
added function for reading RSSI from a analog singal (with RC-Filter)
Coding style and clean up
Merge pull request #165 from xeno010/dev-rssi-adc

Added function for reading RSSI from a analog singal (with RC-Filter)
support for manually setting sbus offset, for FrSky receivers, or in general allowing to adjust output center.
Merge branch 'master' of https://github.com/multiwii/baseflight