[SPARK-4671][Streaming]Do not replicate streaming block when WAL is enabled

Currently streaming block will be replicated when specific storage level is set, since WAL is already fault tolerant, so replication is needless and will hurt the throughput of streaming application.

Hi tdas , as per discussed about this issue, I fixed with this implementation, I'm not is this the way you want, would you mind taking a look at it? Thanks a lot.

Author: jerryshao <saisai.shao@intel.com>

Closes #3534 from jerryshao/SPARK-4671 and squashes the following commits:

500b456 [jerryshao] Do not replicate streaming block when WAL is enabled
[SPARK-4606] Send EOF to child JVM when there's no more data to read.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #3460 from vanzin/SPARK-4606 and squashes the following commits:

031207d [Marcelo Vanzin] [SPARK-4606] Send EOF to child JVM when there's no more data to read.
[SPARK-4860][pyspark][sql] speeding up `sample()` and `takeSample()`

This PR modifies the python `SchemaRDD` to use `sample()` and `takeSample()` from Scala instead of the slower python implementations from `rdd.py`. This is worthwhile because the `Row`'s are already serialized as Java objects.

In order to use the faster `takeSample()`, a `takeSampleToPython()` method was implemented in `SchemaRDD.scala` following the pattern of `collectToPython()`.

Author: jbencook <jbenjamincook@gmail.com>
Author: J. Benjamin Cook <jbenjamincook@gmail.com>

Closes #3764 from jbencook/master and squashes the following commits:

6fbc769 [J. Benjamin Cook] [SPARK-4860][pyspark][sql] fixing sloppy indentation for takeSampleToPython() arguments
5170da2 [J. Benjamin Cook] [SPARK-4860][pyspark][sql] fixing typo: from RDD to SchemaRDD
de22f70 [jbencook] [SPARK-4860][pyspark][sql] using sample() method from JavaSchemaRDD
b916442 [jbencook] [SPARK-4860][pyspark][sql] adding sample() to JavaSchemaRDD
020cbdf [jbencook] [SPARK-4860][pyspark][sql] using Scala implementations of `sample()` and `takeSample()`
[SPARK-4881][Minor] Use SparkConf#getBoolean instead of get().toBoolean

It's really a minor issue.

In ApplicationMaster, there is code like as follows.

    val preserveFiles = sparkConf.get("spark.yarn.preserve.staging.files", "false").toBoolean

I think, the code can be simplified like as follows.

    val preserveFiles = sparkConf.getBoolean("spark.yarn.preserve.staging.files", false)

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #3733 from sarutak/SPARK-4881 and squashes the following commits:

1771430 [Kousuke Saruta] Modified the code like sparkConf.get(...).toBoolean to sparkConf.getBoolean(...)
c63daa0 [Kousuke Saruta] Simplified code
SPARK-4297 [BUILD] Build warning fixes omnibus

There are a number of warnings generated in a normal, successful build right now. They're mostly Java unchecked cast warnings, which can be suppressed. But there's a grab bag of other Scala language warnings and so on that can all be easily fixed. The forthcoming PR fixes about 90% of the build warnings I see now.

Author: Sean Owen <sowen@cloudera.com>

Closes #3157 from srowen/SPARK-4297 and squashes the following commits:

8c9e469 [Sean Owen] Suppress unchecked cast warnings, and several other build warning fixes
[SPARK-4873][Streaming] Use `Future.zip` instead of `Future.flatMap`(for-loop) in WriteAheadLogBasedBlockHandler

Use `Future.zip` instead of `Future.flatMap`(for-loop). `zip` implies these two Futures will run concurrently, while `flatMap` usually means one Future depends on the other one.

Author: zsxwing <zsxwing@gmail.com>

Closes #3721 from zsxwing/SPARK-4873 and squashes the following commits:

46a2cd9 [zsxwing] Use Future.zip instead of Future.flatMap(for-loop)
[SPARK-4953][Doc] Fix the description of building Spark with YARN

At the section "Specifying the Hadoop Version" In building-spark.md, there is description about building with YARN with Hadoop 0.23.
Spark 1.3.0 will not support Hadoop 0.23 so we should fix the description.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #3787 from sarutak/SPARK-4953 and squashes the following commits:

ee9c355 [Kousuke Saruta] Removed description related to a specific vendor
9ab0c24 [Kousuke Saruta] Fix the description about building SPARK with YARN
Fix "Building Spark With Maven" link in README.md

Corrected link to the Building Spark with Maven page from its original (http://spark.apache.org/docs/latest/building-with-maven.html) to the current page (http://spark.apache.org/docs/latest/building-spark.html)

Author: Denny Lee <denny.g.lee@gmail.com>

Closes #3802 from dennyglee/patch-1 and squashes the following commits:

15f601a [Denny Lee] Update README.md
[EC2] Update default Spark version to 1.2.0

Now that 1.2.0 is out, let's update the default Spark version.

Author: Nicholas Chammas <nicholas.chammas@gmail.com>

Closes #3793 from nchammas/patch-1 and squashes the following commits:

3255832 [Nicholas Chammas] add 1.2.0 version to Spark-Shark map
ec0e904 [Nicholas Chammas] [EC2] Update default Spark version to 1.2.0
[EC2] Update mesos/spark-ec2 branch to branch-1.3

Going forward, we'll use matching branch names across the mesos/spark-ec2 and apache/spark repositories, per [the discussion here](https://github.com/mesos/spark-ec2/pull/85#issuecomment-68069589).

Author: Nicholas Chammas <nicholas.chammas@gmail.com>

Closes #3804 from nchammas/patch-2 and squashes the following commits:

cd2c0d4 [Nicholas Chammas] [EC2] Update mesos/spark-ec2 branch to branch-1.3
Delete obsolete mapReduceTripelets used in Pregel
Fix API to retain binary compatibility