[PATCH] Support conjunctive keyword search in RPC interface

[Kevin Morris]

Alright, patch sent; I used `-v1` this time with `git send-email`... I
can't find documentation for that switch yet. I've tested basic search
through both paths; the only refactoring that needed to be done was to
remove the extra "AND (" and ")" from the generic function, and add it
where we need it in `pkg_search_page`. Then, we can reuse the same
`construct_keyword_search` in rpc.