Custom Loading Screen

Many changes:

* Allow using "config:" to load from the config directory rather than a resource pack

* Fixed the way that all locations apart from "TOP_LEFT" worked.

* Added a "scale" property to text

* Added "sample/slideshow" to show a slideshow of images from "config/customloadingscreen/slideshow_#.png"

* Added tip loading from "config/customloadingscreen_tips.txt"

* Made animated images work. Hopefully? (Assuming they were broken before, which they might not have been).

* Added a new sample config: "sample/panorama_lower"

* Broke sample/rotating_cakes :/