CowDb 2, COODBMS 0.5

The simplified API is in place. In the process of doing the release, I found 4 bugs relating to the b-tree logic. Two I fixed, but the other two were in the iterator's remove method which I disabled. On reflection, I now see how I can now implement that remove iterator.

Overall, not the nicest of days. But it is always good to find bugs.

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OK, the remove method been fixed now, tested and checked in. It'll be included in the next release. I'll note that the workarounds were not the fastest approach, so it is good to go back to using the iterator.remove method.