report swift global statistics to statsd

introduce a new script using python-swiftclient to report the statistics, which
also clears up the previous confusion between "global" statistics which are
really per-account, hence the name. the script can also report container stats,
useful for finding out what container is using a lot of space.

puppet side, live with the ugly copy/paste for now as cleanup of this mess will
happen RSN. in the crontab, instead of commandline arguments, drop credentials
into a file to be sourced by swift-account-stats (note the variable names are
the same as the official swift client, thus can be safely reused)

Change-Id: Ifb267713858e0893e83082bc2ac3ce761b53d7e3