[TW-1250] Activity log report

_Pedram H on 2011-06-10T00:19:19Z says:_

I found that it is very useful to have a activity log report to highlight following items per day:
* Added tasks
* Changes in the tasks (project, priority, recurrence, date, all other attributes)
* Completed tasks

It shows a clear picture of someone's actions in chronological order.

A good example of this feature can be seen in http://taskwarrior.org/projects/taskwarrior/activity .

Hint: I think presenting the information inside *undo.data* file show provide this feature.