Site search now handles domains, published snapshots, and unpublished snapshots appropriately

Fixes #3639 
FogBugz ticket here:
http://manage.dimagi.com/default.asp?118826#679717
I'm with you on that one, but in this case it looks like he copied the syntax from the other cases - they all use

    elif doc_type in <doc type tuple>:

I know a foolish consistency is the hobgoblin of simple minds, but in this case I think keeping it uniform makes the most sense.