Improve ebs_volume prune action. Allow to set a number of periods to keep snapshot within.
Periods :
hourlies - how many hours need to keep one snapshot per hour,
dailies - how many days need to keep one snapshot per day,
weeklies - how many weeks need to keep one snapshot per week,
monthlies - how many months need to keep one snapshot per month,
yearlies - how many years need to keep one snapshot per year.