Cycles / Tile Rendering:
* Added new option to chose the tile order.
In addition to the "Center" method, 4 new methods are available now, like Top -> Bottom and Right -> Left. 

Thanks to Sergey for code review and some tweaks! 

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53639 954f8c5b-7b00-dc11-b283-0030488c597c