Car dealerships should be visible earlier in tiles

[nvkelso]

This area of Colma along Serramonte Blvd is known as "auto row" and is a regional attraction. But these features aren't visible until zoom 17. We should include them earlier, based on their areas.

The Lexus dealership in the huge building is a candidate for z14. The nearby Cadilac dealership at z15, the others (example) at z16 (change the no-area default from 17).

Related: #520

17/37.67391/-122.46187