[RFC] Breaking API Changes

[Ufuk Celebi]

I would like to request some further comments on the following two issues:

- FLINK-1023: https://issues.apache.org/jira/browse/FLINK-1023
- FLINK-848: https://issues.apache.org/jira/browse/FLINK-848

The 0.6-incubating release is a good opportunity to fix these.