Add precondition check: this feature is optional. Implementing classes can return NULL if not use
- change to use new feature if_not_exist of CQL 2.0
- change to use new feature if_not_exist of CQL 2.0
- change to use new feature if_not_exist of CQL 2.0
- change to use new feature if_not_exist of CQL 2.0
revert
use map type to fix duplication
Updating pom to SNAPSHOT