Add orthographic and axis lock features to the 3D view

[abey79]

An orthographic projection of a 3D scene with well-defined axes can sometimes usefully complement our current user-controlled perspective view. For example, this would enable replicating the perspective/front/left/top views of CAD software:

This would be extending the 3D view with options to:

• set the projection to ortho
• partially restrict the view-eye control, e.g. locking it's orientation (the user would retain the ability to pan and zoom)
• fully restrict the view-eye, for a total control of the display

Note that a 3D view with ortho + locked axes is technically similar to our 2D viewer, so extending it instead might enable similar end results.

Potentially relates to:

• Configurable extent of 2D space views #683
• Configurable ranges / (spatial) extent in image and tensor view #1510
• Log 2D -> 2D transformations in the transform hierarchy #349

[SeaOtocinclus]

Would be very useful for all mapping (i.e show BBox or point cloud on top of existing 2D maps) related display!

[mont1004]

Hi there!

I'm really looking forward to this feature. While having projection with well-defined axes is nice, just being able to switch to ortho projection is highly valuable for me. If it's relatively simple to implement just that feature, would it be possible to introduce just the projection method switching functionality a bit earlier?