Ordinarily the limit defaults to user preference, but it can be
overridden by the query string itself. This is common in dashboard
queries. Users who follow the linked section headers in the dashboard
get confused by the pagination because each page skips many results.
To fix this, we use a regex to look for limit:N in the query. If
present, the value given in the query overrides the user preference when
computing the navigation links.
Bug: Issue 6716
Change-Id: I1c20913634e3cf8fbe98b24d5c166b66287043be
29693ac125