Collect statistical data from authoring engine (second part)

- added sample duration to the statistcal log messages.
- fixed the bug on miscalcuting the average frame rate.

- also fixed an issue where both frame and time progress status notifications
  are sent out even though only one of them is explicitly requsted.

Change-Id: Ib86f15a85fad3dbeabde120c3c782b79c16da46c