Add big misses for all years

[Damonamajor]

Finding erroneously priced sales led to issues such as #311, where we tried to identify incorrect data. This creates a new table which looks at all sales, and identifies the largest and smallest decreases in FMV to Sale Price (organized by township).

In essence, if we find a sale where the difference is $20,000,000, even if the sale was in 2018, that would be a pin where we might want to investigate if it should be an outlier / if something was input incorrectly.