itemActivityLogForAllItems: disallow requests for too many items and too many groups

[zenovich]

Without such a restriction, it may take too much time to get the needed data from the DB, but the returned data is not very helpful: it returns first 20 rows of something like 580,215 activities of 340 participants related to 1,413 items (just the first one of 29,011 pages!)
See #987 (comment) & #987 (comment) for details.