Three Normal Forms tutorial revised

After two months in the wilderness, my tutorial on the Three Normal Forms is back online.

I took it down because in the original, it had some serious flaws. While not factually inaccurate, the section pertaining to NF1 was vague and misleading, and actually belonged in the NF2 section. I have corrected and expanded the NF1 discussion, and I hope I have not obscured the simplicity of the original tutorial.

Thanks especially to Richard Moignard whose helpful feedback finally inspired me to make the changes.