OBJ_LOADER_DEMO: Generate all the lights
OBJ_LOADER_DEMO: Add a cube to the scene

Later, we will create multiple instances to test instance code
OBJ_LOADER_DEMO: Create utility functions for creating matrices from vectors
OBJ_LOADER_DEMO: Rename the input layout to signal that it is agnostic to render type
OBJ_LOADER_DEMO: Give forward vertex shader its own constants

While it's perfectly fine to share with gbuffer shader, since they're never used
at the same time, it was confusing to see the c++ shader definition with no
cbuffers, yet the hlsl clearly has a cbuffer.
OBJ_LOADER_DEMO: Rename function to better describe what it's for