Blender Git Loki

Viewport: use depth shader to debug the depth

At the moment this already shows that the depth is the same after the solid plates and in the very end of drawing, while they should be different. Later on we can adapt this to show different buffers we want to debug.

I am using near=0.1, far=2.0 for my tests. I decided not to make a doversion for near/far because this is for debugging only