Reduce graphite's stats retention policy

In order to make more efficient use of disk space, let's change the
default retention policy. Being able to react to changes with a
10-seccond precision less likely to be usefule as the data gets older,
and our historic data does not give much insight beyond a 1-hour
precision.

This change does not effect already created metrics, changing that would
require a manual run of whisper-resize.py on the data directories. This
only effects new metrics.

Old retention:
  10-second precision for 6 hours
  60-second precision for 7 days
  10-minute precision for 5 years

New retention
  10-second precision for 8 hours
  60-second precision for 7 days
  1-hour precision for 1 year
  1-day precision for 5 years

Change-Id: I08d73d092fc73c271e9092f551f38f395e006ca4
Merge "Reduce graphite's stats retention policy"