Add support for --timing options. Use cliff via a pseudo-command
'Timing' to support multiple outputformats.
If an output format other than the default 'table' is selected
use CSV since the timing data is in list form.
Will pick up timing data for any client object that has a method
similar to novaclient's get_timings().
TODO:
* Stop instantiating all of the clientmanager client objects just
to check for timing data. Descriptor magic required?
Change-Id: I7f1076b7a250fba6a8b24b2ae9353a7f51b792b2