Use tuple as the default storage format.

I think parseSQL does return key_and_row by default. The reason I have to set key_and_row here is that I use StorageFormatRegistry#getDefaultStorageDescription if the storage is null, and that doesn't set key_and_row to any value (though I think it could, if that would be preferable).

Ideally I would call StorageFormatRegistry#finishStorageDescription here, but it required an FDBNameGenerator and I didn't see a way to get that working.