List bad DVM kinds for people to avoid

[dtdannen]

Currently these kind numbers are being used for other things and it would be nice to let devs know to avoid them. Even though they are within the 5000-5999 or 6000-6999 range, they are not DVM events. Current list that I know about:

• 5666/6666 - ignore because 6666 is being used for something else
• 5969/6969 - ignore because 6969 is being used for polls

I considered adding them to the kinds/ folder but since they aren't DVM kinds, but a simpler idea would be to make a single list somewhere.