[bug 1100394] Implement simple_query_search in Advanced Search.

This was pretty easy. I still need to decide where the documentation should go. I kind of think it should be a KB article linked right from an (?)icon to the right of the search box.

Anyway, r?.

The one minor issue here is that this is using snowball to do stemming and stop words, but the data in the index uses locale-specific analyzers. Thus it's entirely possible to have a mismatch in stemming which would lead to "incorrect results".

I don't know if I can think of a good example of that, nor do I have a clue whether that'll come up much.

I think I'd either address it here by using a locale-appropriate analyzer or I'd throw in a "FIXME" comment.