Image and Entity Changes

Added a resource management system for images, thus creating a central
repository from which the game can access all of it's image resources,
and reduce hard disk usage.

The very basics of game play have been added now. The "Start Game"
button now works, spawning in a player entity in a blank realm. The
player can be moved, and it's collision logic is complete, being fully
compatible with window resizing.

The background color of the particle engine has been changed to a
slightly blue hue.