Cleanup v1 vestigaes and simplify v2 api

Remove v1 entities and concepts
Remove abstractions needed to support v1 along with v2.
Simplify v2 api as a follow through on v1 cleanup.

- Remove ServiceConfiguration. Clients should now directly use CloudServiceOffering (which they were earlier getting through a ServiceConfiguration.getServiceOfffering()). Associated getServiceConfigurations() replaced with getServiceOfferings().
- Remove framework and runtimes. Change the defintion of Staging to include buildpackUrl (in addition to already existing "command").