Added event notification system.
Added a window class.
Created button class, moved interactable.h
Moved window class to interface folder.
Added a click event to buttons.
Fix for crash when adding event listeners.
Added a graphic to the fighters list button.
Use button class for buttons.
Create a window
Generalise the InteractableManager.
Added RenderableManager class.
Fighters button toggles fighters menu.
Moved game map parsing to separate function.
Added Settings class, accessible from lua.
Move most classes in gfx namespace outside it.
Fixed bug where manager class was being accidentally passed by value.
Moved Entity, Grid classes, created Task system.
Print opengl version
Depth rendering through sorting.