1) config cannot be resolved
2) The method registerProviderType(int, Class<? extends WorldProvider>, boolean) in the type DimensionManager is not applicable for the arguments (int, PlanetWorldProvider, boolean)
Come on dude, this is basic stuff; basic Java, casting.
1) The code doesn't even know where "config" is. Where you load your config, and save you config is where you should put it. Why put it in load, when Forge doesn't even read it?
2) Class<? extends WorldProvider> (does not equal) PlanetWorldProvider. You need to make your PlanetWorldProvider "extend" WorldProvider.
One more thing, you don't even know how to use configs. You have to create a new instance of the int in your mod, and set the value later. You can't even receive (ExoplanetaryExploration.config) because it isn't static. Please please please, don't come here until you fully understand how casting works and how fields work.