Adding intial compute service client. Adding support for listing and getting flavor information
Added unit tests for the new compute service client
Refactoring the StorageServiceClinetContext to be a generic ServiceClientContext
Created a base class for service clients in order to maximize code reuse.

Partially implements blueprint support-compute-api
Change-Id: Ibf22961dfc5f957d7acfa9f3159e6bd092459db9