Suggestion: distinguish between Creative and Survival modes

It would be great if one could distinguish between Creative and Survival modes while using Custom Stuff (for example, a tool that should behave differently when used in either mode).

Should probably be ScriptableWorld method, something like: boolean isCreative() - returns true if we are in creative mode, false if in survival

(I know, adventure mode is planned, but let's not worry about that until it arrives ;) ).