Blender Git Loki

Add Object Tool: support placing objects in orthographic axis views

When an projecting onto a plane that is orthogonal to the views Z axis,
project onto a view aligned axis then map it back to the original plane.
see: ED_view3d_win_to_3d_on_plane_with_fallback

Since the depth can't be properly visualized in 3D, display a 2D so
it's possible to to tell the depth from the cursor motion.