Recent vulkan validation layers started complaining about vertex
processing stages having read-write buffers without atomics enabled
(fair enough), but I decided to get all the buffers that don't need to
be written.
This allows the use of an entity id to index into the entity data and
fetch the transform and colormod data in the vertex shader, thus making
instanced rendering possible. Non-world brush entities are still not
rendered, but the world entity is using both the entity data buffer and
entid buffer.
