multirotor_attitude_control performance improved, tested in flight. PID library new functionality and bugfixes.
Copyright fixes
sdlog2: FLOW message added, bug fixed in optical_flow topic
sdlog2: bugfix in FLOW message
Merge pull request #315 from DrTon/sdlog2

sdlog2: FLOW message added
Added global position to logging
Merge pull request #318 from PX4/global_pos_log

Added global position to logging
Merge pull request #314 from DrTon/att_control_der_fix

Multirotor attitude controller updated
merge upstream/master