Add role v3 support to identity in openstack client

Added create/delete/set/list/show support for roles
Broken up to make reviewing easier.
Will add more functionality (add/remove) later

Change-Id: I95bddd27d8d9d251ad2fd60c3e3ee1e2cbcd7d4b
Removed unused imports.

Change-Id: Ib1bae16f996559c008fb1fe0b74f26b152854ea8
Merge "Add role v3 support to identity in openstack client"
Merge "Removed unused imports."