This adds wrapper classes that make it easier to use GPU objects in C++.
####Motivations:####
- Easier handling of GPU objects.
- EEVEE rewrite already makes use of similar wrappers.
- There is the ongoing effort to use more C++ in the codebase
and lans to port more engines to it.
- The shader code refactor will make use of many UBOs with shared
struct declaration. This helps managing them.
- Safer handling of `TextureFromPool` which can't be bound as normal
texture (only texture ref) and can be better tracked in the future.
####Considerations:####
- I chose the `blender::draw` namespace because `blender::gpu` already has private classes (i.e: `gpu::Texture`).
- Theses are wrappers that manage a GPU object internally. They might be confused with actual `Texture`. However, the name `TextureWrapper` is a bit too much verbose in my opinion. I'm open to suggestion about better name.
Reviewed By: jbakker
Differential Revision: http://developer.blender.org/D13805
ec5560db73