Merge branch 'navigator_rewrite' into navigator_rewrite_drton
Support for List, Open, Read, Terminate commands

Fixed various bugs. Flattened Mavlink::Session class while fixing bugs
in this area.
Merge pull request #1083 from DonLakeFlyer/mavlink-ftp

FTP List, Open, Read, Terminate commands working end to end with QGC
estimator: Fix minor reporting issues
Remove old TECS implementation - we can really only decently flight-test and support one.
geo lookup lib: Moved to separate module and compiling with -Os to save some precious flash
Comment fix in perf counter header, no code changes.
Enable new lookup lib
Merge pull request #1085 from PX4/geo_flashefficiency

geo lookup lib: Moved to separate module and compiling with -Os to save ...
Merge pull request #1084 from PX4/mtecs_pure

Remove old TECS implementation - we can really only decently flight-test...
Merge remote-tracking branch 'upstream/master' into mtecs
Merge remote-tracking branch 'upstream/mtecs' into navigator_rewrite
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.