Reordered execution and removed GL thread queueing in Mission.
Separated constructor and level loading in OverworldSystem.
Refactored visibleWorldObject to nearbyWorldObjects, removed visibility
constraint from nearbyWorldObjects in RenderList.
Refactored getCurrentRenderList() to currentRenderList().get() in
Renderer.
Additional null checking of altitude map in CollidesWithTerrain.
Incremental implementation of new texturing system.
Removed redundant player tick() invocation in ThreadManager.
Added boundary checking for code pages in VQCodebookManager.
Wrapped GLTexture.setTextureRGBA() into GL thread task.