Improve handling of new construction and divisions

[dfsnow]

The condo model currently handles new construction the same way it handles any other property: by using sales to predict the value of unsold properties. This method doesn't work well for new properties because the sales are inevitably higher than similar non-new properties.

We should add flags and/or a separate valuation methodology for new construction condos. Specifically, we should look for new 299 PINs resulting from divisions and 297 PINs that become 299s. We should also flag large YoY drops in building price, as this can be an additional indicator of misvalued new construction.

Note that for the under construction 297 or 299 PINs may not be the same as the final 299 PINs.