Closes #432

- this implements two convenience methods on DataSet for the Java and Scala API
- appropriate tests have been added

count(): returns the number of elements in a DataSet
collect(): returns a List<T> with the actual elements of a DataSet<T>

- both methods use accumulators to get the results back to the client
- both methods force an execution of the job to generate the results

This closes #210

This closes #430

The PipelinedPartitionQueueTest spuriously fails with a timeout. It is unclear
whether this is due to a deadlock or a test environment hickup. Since build
artifacts like stack traces for stalled builds are uploaded to S3, we can let
this test deadlock (if it is one) and then start debugging. ;-)

This closes #424

This closes #435.

This closes #438.

This addresses PR comments: https://github.com/apache/flink/pull/436/

[FLINK-1607] [runtime] Moves PartialPartitionInfo from ExecutionVertex to Execution to automatically clear them in case of restart

This closes #436.

Replaces recursive concurrent modification resolution by while loop

Turns off stdout-logging of Akka. Sends proper exceptions in ErrorResponse.

Proper stream closing

[FLINK-1607] [tests] Fixes SimpleRecoveryITCase by rebalancing the data sources so that all mappers receive at least one element

[FLINK-1606] [tests] Fixes JobManagerFailsITCase for Akka 2.2.1 by setting gate-invalid-address-for = 5s and quarantine-systems-for = off

package statement was not updated after class movement
also added a missing import

Author: mjsax <mjsax@informatik.hu-berlin.de>

Closes #437 from mjsax/bug_fix_package_statement and squashes the following commits:

1470b0f [mjsax] fixed package statement

[FLINK-1580] [FLINK-1590] [runtime] Various cleanups and improvements in the TaskManager initialization

 - Better checks during TaskManager startup
 - More robust initialization of TaskManager actor system and actor
 - Fix memory accounting during TaskManager startup
 - Better logging for TaskManagers started through YARN
 - Remove command line parameter hacking fro YARN TaskManagers

Also adds various tests for failure behavior during job submission.

[FLINK-1598] [runtime] Better error message when network serialization of records exceeds java heap space.

This closes #431

[FLINK-1515] [gelly] Changed PageRank to use broadcast set provided by numberOfVertices() to read the number of vertices instead of passing it to the constructor.

This closes #402

[FLINK-1515] [gelly] Splitted runVertexCentricIteration into createVertexIteration and runVertexIteration to make VertexCentricIteration object accessible to developers.

Before, translateToDataflow of SingleInputOperator could only return
a single input operator of the lower layer, same for TwoInputOperator.

This change allows translateToDataflow to return more kinds of
operators.

This closes #428.