refactor pagination

[misch]

1. Pagination of search results in controller. Admittedly, pagination is a UI concern, not a pure model concern. Still, the logic could be encapsulated into a "helper" SearchResult object, that knows how to return individual pages of results. It should at least be in a function that extracts one page from the list. Same for user list display.
2. Same for the listing of active/inactive items. The pagination logic should be factored and reused, both for less fragility of the code, and better readability.
3. Other similar cases.