Blender Git Loki

Overlay Engine: Empties

Overlay Engine: Add Camera & Stereo Camera

This change a few thing:
- This fixes the toe-in convergence plane drawing issue.
- The volume wires are drawn without depth write to avoid Z-fighting.

Overlay Engine: Fix light distance display scalling with object size

Overlay Engine: Separate GroundLine/Point to a separate buffer

Fix compilation error

Overlay Engine: Add Lamps

Overlay Engine: Add Edit Mesh

Overlay Engine: Add Outline

Overlay Engine: Add Grid

Overlay Engine: Initial Commit

This merges all overlay draw engines into one unique engine.

The goal here is to have more flexibility on how to draw overlays and
overcome some of the current design limitation.