Add the configuration of the name of the stats.

By default it's now nova.hypervisor_stats and this can be changed using
SpaceName configuration.
Change SpaceName to more meaningful MetricName.
Add floating ip metering.
Update the README.
Clean spaces.
Rename metric to openstack.<cmpnt>.<stat> scheme.
Fix type in neutron floating ip.
Adding collectd-cinder stats.
Add README.
Rename volumes to cinder.
Adding basic keystone metrics.
Fix copy/paste error in the readme.
Add readme for keystone.
Lint cinder stats.
Lint keystone stats.
Lint neutron floating ips.
Lint nova hypervisor stats.
Improve error handling for keystone plugin.

Now we raise a exception.  It enables collectd to detect the problem.
It then put the plugin to "sleep" in a exponential backoff style.
Before that a error message would fill the log every time collectd ran
the plugin.
Fix linting of nova plugin.
Remove useless variable in keystone.