Blender Git Loki

Cycles: Change several default values (first batch).

This changes the following defaults:

- Render settings:

* Samples: 100
* Preview Samples: 50
* Filter: Blackmann-Harris
* Tile Order: Hilbert Spiral

- Lamp settings:

* Use MIS: On

- Material settings:

* Volume Sampling: Multiple Importance

Old files are not affected, I tested the versioning code back and forth.
More changes are to come (World, BVH...) but that needs a bit more work.