Pagination on place_detail page can skip items

[slinkp]

Place detail page does a sort of pagination by date; see eg. http://demo.openblockproject.org/locations/zipcodes/02116/ and note the "older news" link at bottom.

When there's a lot of news, the "older news" link can skip some items.

Why:

The page by default shows 7 days of news (or settings.DEFAULT_DAYS). At page bottom is an "older news" link. It links to the day before the last day shown on this page. That's fine if the page is showing all news within that date range. Problem is, the database query is also capped at constants.NUM_NEWS_ITEMS_PLACE_DETAIL, which is 300 by default. If you hit that cap before you get to the end of a day's worth of news, the rest of the news from that day will be skipped when you follow the link to the next day.

Example:

• It's a busy week. Let's say that exactly 123 news items happened each day this week. (That's not unreasonably high; I've seen more than one scraper log hundreds of items in one zip code per day.)
• The place detail page for that zip code cuts off at 300 items. That's 123 items from the first day, 123 from the second day, and 54 from the third day.
• The link at bottom of page takes you to day before the last item shown - the fourth day.
• There are 46 items from the end of day 3 that are not shown on either page.

[slinkp]

(In [2b33d1b3cf080a20006b389147cd3720b5478afc]) Place detail page: Use page-number-based pagination, not date-based. Fixes #282.

[slinkp]

Ticket imported from Trac: http://developer.openblockproject.org/ticket/282 Reported by: slinkp