Implement a rough CLI foundation

This is a foundation for CLI work, still has rough spots but works for
two PoC commands - rack-list and rack-show (communicates with Tuskar,
prints). There's remaining stuff to be solved:

* Allow arbitrary formatting of attributes (bug #1213056)

* Add help support for subcommands (bug #1213050)

* Allow finding resources by name (bug #1213053)

* Allow auth with pre-existing token and Keystone URL (bug #1213052)

Fixes bug #1211826

Change-Id: I9364be37c7111c85ef46be82b157782a14743004