Added NEI compatibility for the Cupola

Other devs will need to add NEI to their build path or they'll have errors in the workspace (if not, the game will still load just fine, since NEI won't be present so the errors will just get ignored)

Sorry if this is not wanted, just thought it would be a nice addition to have this already in the mod :)

It won't depend on NEI to launch, NEI automatically finds the NEISteamNSteelConfig class and loads it up. If NEI isn't present that class will just never be loaded.

Fixed the build.gradle file to automatically download NEI and add it to the dependencies, so building the mod is still exactly the same.