Merge remote-tracking branch 'upstream/navigator_rewrite' into navigator_rewrite_estimator

Conflicts:
	src/modules/ekf_att_pos_estimator/ekf_att_pos_estimator_main.cpp
att pos estimator: silence annoying messages
Fix compile warnings in estimator
Define earth radius as double, as our calculations relying on it need double precision.
More safe compile warning fixes
Merge pull request #1081 from PX4/hb_fix2

mavlink: init structs for HEARTBEAT if uORB topic copy failed
Estimator: Clean up delta quat calculations, put them in a sweet spot between accuracy and runtime.
Observation index cannot get negative.
estimator: Fix double promotion warnings by appropriate constants / casts.
estimator: Geo conversions: Fix float / double types to prevent warnings. Fix calcLLH to actually return a value.
estimator: Move symmetry force outside of non-related loop, improving efficiency and resolving a locals warning.
Merge pull request #1063 from pigeonhunter/offset_tuning

Offset tuning implemented in sensors app
Merge pull request #1037 from PX4/mtecs

mTECS
Merge pull request #923 from PX4/mavlink-ftp

Mavlink File Transfer Protocol (FTP)
fw att ctrl: resolve warnings
Merge pull request #1088 from PX4/fwattwarnings

fw att ctrl: resolve warnings
estimator: Fix local variable compile warnings.
Merged master
navigator: whitespace fix
Merged master into navigator_rewrite