[tests] Replaces Scala mixins for the Job/TaskManager with classes which extend the respective classes. Adds proper logger registration for sub-classes of FlinkUntypedActor.

This closes #1022

This closes #1004

This closes #977

[tests] Hardens TaskManagerRegistrationTest.testTaskManagerResumesConnectAfterJobManagerFailure test case by checking testing actor's complete mailbox for a Terminated message

Closes #1025

Closes #1014

Closes #994

[FLINK-2521] [tests] Adds TestLogger class which automatically logs the currently executed test names and the reasons for a failure.

Makes test bases extend TestLogger to add automatic test name logging

Frames test logging statements to make them more prominent

This closes #1015.

[tests] Reinforce StateCheckpoinedITCase to make sure actual checkpointing has happened before a failure.

[FLINK-2462] [streaming] Major cleanup of operator structure for exception handling and code simplication

  - The exceptions are no longer logged by the operators themselves.
    Operators perform only cleanup in reaction to exceptions.
    Exceptions are reported only the the root Task object, which knows whether this is the first
    failure-causing exception (root cause), or is a subsequent exception, or whether the task was
    actually canceled already. In the later case, exceptions are ignored, because many
    cancellations lead to meaningless exceptions.

  - more exception in signatures, less wrapping where not needed

  - Core resource acquisition/release logic is in one streaming task, reducing code duplication

  - Guaranteed cleanup of output buffer and input buffer resources (formerly missed when other exceptions where encountered)

  - Fix mixup in instantiation of source contexts in the stream source task

  - Auto watermark generators correctly shut down their interval scheduler

  - Improve use of generics, got rid of many raw types

This closes #1017

This closes #1029

This closes #1018

[FLINK-2527] [gelly] Ensure that VertexUpdateFunction.setNewVertexValue is called at most once per updateVertex

This closes #1027

[FLINK-2458] [FLINK-2449] [runtime] Access distributed cache entries from Iteration contexts & use of distributed cache from Collection Environments

This closes #970

This closes #1021

This closes #1009

PlanBinder methods were restructured to make the class more readable.

Keys are now stored as strings to simplify string-key-expression support.
Parameter retrieval was moved from PB to OI constructor, similiar to PythonOperationInfo.
This change reduces the clutter in Planbinder and allows code reusage for operations with similar parameters.

This closes #961

 - extended TupleType helper classes to handle Tuple0
 - extended TupleSerializer to handle Tuple0
 - included Tuple0 into JUnit tests
 - simplified Receiver.createTuple(int)

This closes #983

This closes #1013

Correcting commit, because the wrong commit was pushed earlier.

1. Allow access to Runtime Context from I/O formats.
2. Make all existing I/O formats context aware.

This closes #966.

[CLEANUP] Add space between quotes and plus sign in String concat for readability in flink-yarn module

While working on Flink on YARN, do some simple nit cleanups to add space between quote and plus sign for readability in yarn module for readability.

Use StringBuilder instad of StringBuffer in FlinkYarnClient since the String materializes immediately, so no need synchronize protection.

Author: hsaputra <hsaputra@apache.org>

Closes #1010 from hsaputra/cleanup_yarn_branch and squashes the following commits:

a6fc9e1 [hsaputra] Add space between quote and plus sign for readability in flink-yarn module.

regression of c6358024

Also changed some prints which printed the word "class" twice,
because class.toString also prepends it to the class name.

This closes #960.

Closes #1007

[FLINK-2509] [runtime] Add class loader info into the exception message when user code classes are not found.

This closes #1008

Closes #980

This closes #1005