osx build, segmentation, CV mode enhancements

Car model release

Merge branch 'master' of https://github.com/Microsoft/AirSim

segmentation APIs, car mesh

reset() API, PythonClient changes

fixed 180 degree depth issue, view mode switching

Car model

simple_flight, linux build, CV images

Last version compatible to Unreal 4.15

Linux experimental build, Mav API fixes