I can't seem to find the guy who made this, There is a url but it's not in English. Anyway, this is a great little tool for making a preset world. You can download it here until I find where I got it from. This is all the info I have at the moment.
Custom Superflat Preset Code Generator v1.0
Made by JiangHR and translated by DJXGAME@MCBBS
Custom Superflat Preset Code Generator v1.0
Made by JiangHR and translated by DJXGAME@MCBBS