Blender Git Loki

fix: Fly Navigation centered in viewport, not in camera view

Summary:
The safe zone, mouse and everything else was relative to the viewport.
It should be relative to the camera 'view' instead.

This problem (noticed while developing the Walk Navigation)
happens when the camera is not centered in the viewport.

Reviewers: campbellbarton

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D78