Blender Git Loki

Tomato Cycles: use actual number of tiles for viewport rendering

Before this debug_tile_size was used as a size of tile, which
became hidden property since tile-based rendering implementation
and couldn't have been controlled.

This resolves the issue with single thread used for viewport
rendering in some cases. Also it makes possible to control tiles
for CUDA viewport rendering, which still behaves much faster when
using the single tile.

Also fixed issue with minimal tile size which was used to calculate
divider of final resolution to be used for initial rendering. Now
it's a Resolution Divider property in Performance tab. This option
could be used to tweak initial resolution of viewport for faster
navigation or faster refresh when changing some properties.