So that the page skeleton is rendered correctly while the graphs are
being loaded.

And put everything in /var/www/html/reports.

New optional tenant_report() parameter 'any_status' ensures that all
status values are looked at.

The table title now includes the sorted set of status values.

Factor out insignificant_usage()

Make ram_cut a class parameter.

Default ram_cut to zero in the main program.

Only call tenant_report() with the (new) default parameters in the
main program.

Convert header comment to documentation strings.

In addition to (Nova) VMs, we now also traverse the list of (Cinder)
volumes for all tenants, and add their sizes to the
tenant/cost-centers' disk usage.

Apparently it's not necessary.

Also, import warnings and use warn() to issue warnings.

Provoke and catch token-too-big errors.

That was just in there to help the programmer.

Works for VMs and their (ephemeral) volumes.

Needs to be extended to handle Cinder volumes (at least).

For extra points: Neutron resources (Floating IPs in particular).
Glance images?