NOTE API change!
 What has changed:
  - Sorting mode Entity API refactor - entity style "sortmode" property renamed to "objectsortmode". The "objectsortmode" now supports 3 values of "sorted", "front", "back" - the 'front' and 'back' values allow objects to be forced to the front or back of the display list.
 Why did it change:
  - Because a future version of Entity will introduce "geometrysortmode" as a way of overriding the default behaviour for sorting of the points/edges/polygons for an entity, renaming sortmode will help avoid confusion with this new property.
 How to migrate:
  - Find and Replace use of "sortmode" property with "objectsortmode"
Improved x2 performance quicksort routine for sorting points coords/worldcoords lists.
Fix to not apply perspective division to z component of NDC coords - improves coarse object sorting so particles always appear in correct depth position relative to other objects.
Simplified and optimized scene processing loop for entity matrix processing. Clearer comments for rendering pipeline calculations.

(svn r631)