Blender Git Loki

Cycles: Initial implementation of detailed statistics

Gathers information about object geometry and textures. Very basic at
this moment, but need to start somewhere.

Things which needs to be included still:

- "Runtime" information, like BVH. While it is not directly controllable
by artists, it's still important to know.

- Device array sizes. Again, not under artists control, but is added to
the overall size.

- Memory peak at different synchronization stages.

At this point it simply prints info to the stdout after F12 is done,
need better control over that too.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D3566