Allows code to directly use GS::Vertex for their own purposes without having to rely on GS::VertexBuffer, which comes with the added overhead of allocating GPU memory.
Changes the GS::VertexBuffer storage to be one continuous buffer that is properly aligned and is also now used for GS::Vertex. This halves the necessary memory, removes reallocation cost and removes the copy necessary to get things onto the GPU.
Related: #9