Revisit condo and multi-sales flagging

[wrridgeway]

Multi-sales are a valuable source of sales information for the condo pipeline, but get a free pass from sales val. Perhaps this has to be the case, but we should at least try to brainstorm some ideas on whether we could validate them so extreme multi-sales don't slip into the condo pipeline.

Additionally, we should review sales val's flagging for condos specifically to make sure it's as accurate and dependable as it is for res.