Minecraft wiki entry for Development_versions, associated text: DataDrivenBlockModels
Added the first pass of the new data driven block tessellation pipelin.
Added the minecraft:geometry component to allow using a block model for rendering.
Added the minecraft:unit_cube component to allow using a default unit cube for rendering. Unit cubes get some extra effects like ambient occlusion and face removal.
Added the minecraft:material_instances component to allow mapping faces and material_instances in a geometry file to an actual material.