[FLINK-4097] Fix NullPointerException on CassandraSinkBase and CassandraTupleWriteAheadSink's close()

This closes #2144

This closes #2111

This closes #2136

Create a task_id message in PythonStreamer that is passed through
to the underlying process and included in the RuntimeContext, where
it is accessible to the user and to functions.

This closes #2130

This closes #2133

By default this is set to disabled because there are known issues when
users specify a custom TypeInformation.

I added this once with the though of varying the start time for window
tests but it just makes stuff harder to parse for now.

These will make it easier to read the tests for our future selves and
others.

In onElement() we registered a timer for the case where the watermark is
already past the end of the window and we're firing anyways. Now, only
add a timer if the watermark is not already past the end of the window.

Handle late elements and take care
of cleaning the window state.

This closes #2132

This closes #2116.

This closes #2117.

This closes #2122

This closes #2119

- setOutputType calls are forwarded to wrapped functions.
- test added for InternalWindowFucntions.

This closes #2118

This closes #1898.

Hardens ZooKeeperElectionTest by allowing the testing listener to return
out-dated leader information. This can happen if the ZooKeeper connection
was suspended and the new leader information has not been sent to the
testing listener. In this case, the testing listener will be queried again
to return the actual leader information.

Add debug statements to ZooKeeperLeaderElectionTest.testZooKeeperReelection

This closes #2103.

Trying to prevent failures like [1] from happening again. I could not
explain who deleted the savepoint file concurrently with the exists
check. The savepoint is triggered and retrieved successfully. Shutting
down the cluster does not remove any savepoints.

[1] https://s3.amazonaws.com/archive.travis-ci.org/jobs/136396433/log.txt

- integrates with and extends the refactoring of FLINK-3667
- enables to resume from Yarn properties or Yarn application id
- introduces additional StandaloneClusterDescriptor
- introduces DefaultCLI to get rid of standalone mode switches in CliFrontend
- various fixes and improvements
- remove legacy code from CliFrontend
- change activation code of CustomCommandLine interface
- use checked exceptions to signal supported operations
- remove all checked exceptions of type Exception
- fix logging and reduce verbosity of per-job clusters
- print 'id' argument in YarnSessionCli
- minor renaming of methods names
- improve documentation
- deprecate streaming option
- extend CliFrontendYarnAddressConfigurationTest
- move loading of custom CLIs to CliFrontend

This closes #2085

- enables to use list, savepoint, cancel and stop subcommands
- adapt FlinkYarnSessionCli to also accept YARN application Id to attach to
- update documentation

This closes #2034

- ClusterDescriptor: base interface for cluster deployment descriptors
- ClusterDescriptor: YarnClusterDescriptor

- ClusterClient: base class for ClusterClients, handles lifecycle of cluster
- ClusterClient: shares configuration with the implementations
- ClusterClient: StandaloneClusterClient, YarnClusterClient
- ClusterClient: remove run methods and enable detached mode via flag

- CliFrontend: remove all Yarn specific logic
- CliFrontend: remove all cluster setup logic

- CustomCommandLine: interface for other cluster implementations
- Customcommandline: enables creation of new cluster or resuming from existing

- Yarn: move Yarn classes and functionality to the yarn module (yarn
  properties, yarn interfaces)
- Yarn: improve reliability of cluster startup
- Yarn Tests: only disable parallel execution of ITCases

This closes #1978

This closes #2107

This closes #2104

This closes #1856

This closes #1771

Introduce timeout handling flag for the NFACompiler

Expose timeout handling via Java API

Update documentation of PatternStream and CEP

Introduce timeout select function to CEP Scala API

Add select and flatSelect with timeout support to CEP Scala API

Add test cases for timeout handling

Update documentation

Fix CEP Scala API completeness test

This closes #2041.

currentLowWatermark
lastCheckpointSize
numBytes(In/Out)(Local/Remote)
numRecords(In/Out)
numSplitsProcessed (Batch only)

This closes #2090