Factored out Actor's getGraphicBounds routines

Factored out Actor's getGraphicBounds routines

- Factored out Actor's getGraphicBounds routines. Was used previously
when shaders were inaccessible to logically alpha blend via composites
entities obstructing camera view. Now that there is shader access, a
more powerful algorithm will be implemented.

- WorldLayer now properly optimizes for Actors that are greater than
1x1. Previous implementation assumed all actors were a tile in width and
height. This meant that if an Actor consumed two or more tiles and
crossed a sector boundary (where only one of the two sectors were
visible), it may have been optimized out of the render routine.

- Removed render splitting, this feature was scarcely used.

- Resolved a few more errors causing vector's sorting model to be lost.

- Added some default implementation to Actor for methods that were
previously purely abstract. This helps remove some boilerplate code.

- General code cleanup.

Jeremy. Allen. Wildsmith