removed api_version in config

Api_version attribute no longer needed in the config. Updated example
attributes to reference.json.config

Rebased with latest changes that split the Images Behavior classes by
API version. Moved get_all_tenant_ids method to TenantBehavior

Renamed behavior methods to follow python convention (no underscore for
public members).

Refactoring for new package structure

Change-Id: I52bc80ad707cbcb8d7c7a18d4b44234f48d44643