Walkabout: loading screens #50
Description
Make a loading screen show whenever a world is being loaded.
We get a .GXA filename from WORLD.INI in the RGINIStore.
This GXA should be shown full-screen when WorldLoader loads a world. UIManager should be able to do this after #40
Ideally, we add a progress bar. Most of the loading progress is being done in ModelLoader.LoadArea(...) so that will need refactoring to regularly send an update back to WorldLoader.
Depending on loading speed, we might want to skip the progress bar.