The current sorting logic of actions in the history is essentially
linear, so that when an action is activated it moves up one place
in the history.  This has the undesirable effect that actions take
very long to climb up the history list, as well as that actions at
the top of the list can change their relative order too frequently.

Improve the sorting logic, such that items climb up the list
faster, while top items retain their relative position longer.  See
the comment at the top of the diff for the actual logic.