SCHEMA-241. Changes ApiAudience to Public for KijiDeleter, KijiIncrement...

...er, and KijiPutter.

Testing done: mvn clean verify

Another straightforward change: Changes some audience annotations and adds a release note for it.

The only subtlety here is whether the javadocs should change. Possibly with a mention of KijiMR as an example of where these are used as well as Writer. Tell me your thoughts.