How to pre-load (lots of) textures in a backgroud thread smoothly

@Escobar there is an idea @Evgeni_Popov posted in Throttle processing power/bandwidth to keep stable FPS during loading - #15 by Evgeni_Popov

TLDR: moving as much of texture loading into a worker as possible. I am still working on this myself, since had other fires pop up that took me off that branch