This closes #3123

This makes InternalWindowFunction subclasses WrappingFunctions and
correctly forwards calls to setOutputType() by unwrapping
WrappingFunction in the newly added StreamingFunctionUtils.

- Make build.sh executable
- Fix Dockerfile using ARG instead of ENV
- Prevent exit only for job-/taskmanger shortcuts

This closes #3086.

To migrate from a RollingSink to a BucketingSink, a
user can now take a savepoint, change his code to
use a BuckeingSink with the same properties as the
previous RollingSink, and resume his program from
that savepoint.

This closes #3102.

The method is not needed and was left there by mistake.

The user can use the deprecated AccumulatingProcessingTimeWindowOperator
and AggregatingProcessingTimeWindowOperator by using the
TumblingAlignedProcessingTimeWindows and the
SlidingAlignedProcessingTimeWindows introduced by this
commit. These operators are neither backwards compatibility
nor rescalable.

This closes #3093.

This closes #3100.

[hotfix] [docs] Move section about internal snapshot implementation from 'state_backends.md' to 'stream_checkpointing.md'

Fixes FLINK-5364, FLINK-5361, FLINK-5350, FLINK-5055

This closes #3057

This closes #3082

This closes #3091

This will also allow for using comma-separated values in the CLI.

This closes #3072

This change makes the code robust against concurrent clock adjustments.

This closes #3044