Added DrawCenteredString static method to SpriteBatchExtensions
Vastly improved HashList DrawDebugInfo function.
Changed prevBoundingBox to PreviousBoundingBox in Entity.
Refactoring. DrawColliderDebugInfo is now performed AFTER
PostGameShaders have been applied.
General Improvements. QuadTree DrawDebugInfo now specifies number of
entities contained within a node.
Random Generation of Bats and Coins now performed on MapLoaded for
example_map
Improvent to HashList DrawDebugInfo code
Changed HashList to use 16x16 Box sizes. Much better CPU time but may be
large in memory.