Blender Git Loki

GPUTexture: Refactor of texture creation & new feature

- Texture creation now requires explicit data type.
- GPU_texture_add_mipmap enable explicit mipmap upload.
- GPU_texture_get_mipmap_size can be used to get the size of a mipmap level
of an existing GPUTexture
- GPU_texture_read let you read back data from a gpu texture.