debugutilsbad: Add timestamper element

Submitted by Nicolas Dufresne @ndufresne

Link to original bug (#797117)

Description

This is a simple element that simply set timestamp based on fixed duration.
The timestamp method could be enhanced later base on needs. This was written
initially to verify if broken or bad timestamp was directly causing some issues
we where observing. It's also handy in some test when pulling some raw frames
from the disk (e.g. multifilesrc). Currently, there is one property "duration".