Changed to yaw only mag correction.
Merge branch 'mag-correct-yaw' of github.com:jgoppert/Firmware into fw_hil_test
Fixed yaw estimate, minor comment and code style improvements. Added option for upfront init, prepared process for removal (later) of sensors app and subscription to individual topics. Prototyping rework of params / subscriptions to resolve GCC 4.7 incompatibility of control lib (or rather the fact that we need to work around something which looks like a compiler bug)
Merge pull request #319 from PX4/kalman_nav

Kalman navigation fixes