Implement emitter feature set (fine-grained emitter control)

[TzuChieh]

Able to fine tune various aspects of an emitter.

• [x] Make BNEEPT respect feature set flags
• [ ] Make BVPT respect feature set flags
• [x] Make photon mapping renderers respect feature set flags (done as this is handled in Emitter and lta)
• [ ] Directly visible should pass through (currently it appears black only)
• [ ] Expose feature set flags for IBL in SDL and Blender
• [ ] Add a render test for diffuse/glossy rendering with different feature set
• [ ] Add a render test for IBL + diffuse/glossy rendering with different feature set