Add an index column to cinder list-functions

Now 'cinder list' only shows the 'ID'/'Status'/'Display Name'/'Size '/'Volume Type'/'Bootable'/'Attached to' columns.

That's OK for normal using.

But if you have more than 200 vols/snapshots in one environment,
'cinder list' will print out lots of lines,
  even if I add some filters (such as '--display-name'/'--status'/..).

It's very hard to count the amount of them.
Like this: http://paste.openstack.org/show/60554/
Now, I just use 'cinder list |wc' to instead (minus 4 line)..

And the 'cinder snapshot-list' has the same situation.

So, if an index column add to list-functions like 'cinder list',
it can easily get the amount of the vols/snapshots which I want to count by given some filtering opinions('--status'/..).