Client interface currently has only one Init method.
Also add a constructor for the Client which is based on resource
defined in clusterctl/api package and a filesystem root to construct
bundle for repository interface. Root is expected to be derived
from the airshipctl settings document manifest.target-path
Factory functions allow to insert custom repository interface
into clusterctl client
Relates-To: #170
Change-Id: Ib27e73043b4776001f405d2d4e96016735c6f46e
b57c1a2d15