[Bf-cycles] Future of the non-progressive renderer and Cycles strand rendering

[Stuart Broadfoot]

My current intention is to work on the following. This is only an 
approximate order though and may change.

- Get curves/ribbons segments working. I have actually already done this but 
it's very slow. I need to experiment with new intersection routines.

- Allow primitive types to be set per particle system and then triangle 
primitives to be used on the GPU.

- Improve the managing of attributes and try to enable the rest of their 
functionality.

- Enable Preview/Render settings

- Add a Hair BSDF

I can't really judge how long all this will take. Once this is done I will 
have a look at further features and optimizations.

Stuart