Search customization per-site

[zerocrates]

Sites give us an opportunity to present more appropriate search pages for each particular site, something we can't do in Classic.

For example, each site could allow configuration of which properties should appear in the search interface. As a shortcut, a query could find each property that's used in any item in the site's pool, and select those properties, but individual one-by-one selection/deselection could also be possible.

Most sites use a very limited subset of the available properties, and S has many more properties than Classic did, so keeping the list of options pared down is more important in S.