sorting and paging mean one list

[pfefferle]

Sorting and paging were plain query parameters, so they belonged to the page, not to a list: on a page with several blogrolls, sorting one sorted all of them and paging one paged all of them. That is the open point from #2.

Every list has an anchor since 1.2.0, and group already uses it for the subscription files, so the sorting and paging links use the same: ?blockroll-sort=name&group=podcasts#podcasts. A list applies the sorting and the paging only when the query names it. A query that names no list still means every list, so links people shared before this keep working.

Tests for both, and I checked it on a page with two lists: sorting one leaves the other alone, each pager pages its own list, and ?blockroll-sort=name without a group still sorts both.

Fixes the remaining part of #2.