wdb, third cut

http://agilewiki.org/wiki/uuid/aI-DsBkGtGYhd1CKY8mPbBEw

Spend the whole day on this. Looking good, if not fully tested.

I've also reworked it quite a bit to work well with longer keys. All in all, its pretty solid.

I did find that larger block sizes slows it down. 512 is a good number for very short keys (which is what I've done the initial tuning with). I think the slow down (in insert speed) may have a lot to do with list insertion, as this version avoids working with strings as much as possible.

Bill