This lets us get rid of m_autorelease and m_destroy and we’ll be able
to implement init_game/init_draw later, for stuff that must happen
on the render thread.
Moved ImageLoader to ResourceLoader, so that loading is extensible.
i.e. here: Zed image loader now loads up a tileset instead of being a
hacked image loader.
Goal is to support more funky stuff (wad, pak .....)