Another version of improved widget of active users

This is the new commit for issue #11107
Now it uses subquery with nested sorting and must work on any type of database.

I have table with 45000 records and when I select last actions for 50 hours this query takes only 0.0287 sec.
Improved groupbe

According to http://dev.mysql.com/doc/refman/5.0/en/group-by-extensions.html
Update widget.grid-online.php
Update widget.grid-online.php
Improved widget of active users

* origin/pr/11244:
  Update widget.grid-online.php
  Update widget.grid-online.php
  Improved groupbe
  Another version of improved widget of active users