Make models follow the glTF spec in that all models should have Y as the up axis. Cesium Man model is still broken.
Fixed Cesium Man model.
Fixed models to use correct up axis.
Brought Cesium Air spec model in sync with the Sandcastle example.
Merge remote-tracking branch 'agi/master' into up-axis
Fixed merging issue.
Added unit test for northUpEast transform and updated the changes.md file.
Fixed Cesium Man one last time.
Merged agi/master into up-axis branch.
Fixed unit tests for northUpEast axes functions.
Merge pull request #1873 from tfili/up-axis

Up axis