Add a `z=N` param to the URL when doing a search from the search box, or
when clicking a link in the tag list. This is to gather data on how
often the links in the tag list are used, and whether it's more common
to click tags in the tag list or to perform searches manually.
This is temporary and will be removed when enough data is collected.
Fix a bug where if you did a slow search that took too long to calculate
the page count, and you had 200 posts per page, then we would show page
5000 as the last page of the search.
This was because we were artificially returning 1,000,000 as the post
count to signal that the count timed out, but at 200 posts per page this
would show 5000 as the last page of the search.
* Refactor the paginator into a ViewComponent.
* Fix inconsistent spacing between paginator items.
* Fix a bug where the sequential paginator generated the wrong next /
previous page links in the <link rel="{next|prev}"> tags in the <head>.
* Always include the final page as a hidden html element, so that it can
be unhidden with custom CSS.
* Make it easier to change the pagination window.
