SPARK-1911: Emphasize that Spark jars should be built with Java 6.

This commit requires the user to manually say "yes" when buiding Spark
without Java 6. The prompt can be bypassed with a flag (e.g. if the user
is scripting around make-distribution).

Author: Patrick Wendell <pwendell@gmail.com>

Closes #859 from pwendell/java6 and squashes the following commits:

4921133 [Patrick Wendell] Adding Pyspark Notice
fee8c9e [Patrick Wendell] SPARK-1911: Emphasize that Spark jars should be built with Java 6.
[SPARK-1886] check executor id existence when executor exit

Author: Zhen Peng <zhenpeng01@baidu.com>

Closes #827 from zhpengg/bugfix-executor-id-not-found and squashes the following commits:

cd8bb65 [Zhen Peng] bugfix: check executor id existence when executor exit
[SPARK-1913][SQL] Bug fix: column pruning error in Parquet support

JIRA issue: [SPARK-1913](https://issues.apache.org/jira/browse/SPARK-1913)

When scanning Parquet tables, attributes referenced only in predicates that are pushed down are not passed to the `ParquetTableScan` operator and causes exception.

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #863 from liancheng/spark-1913 and squashes the following commits:

f976b73 [Cheng Lian] Addessed the readability issue commented by @rxin
f5b257d [Cheng Lian] Added back comments deleted by mistake
ae60ab3 [Cheng Lian] [SPARK-1913] Attributes referenced only in predicates pushed down should remain in ParquetTableScan operator
spark-submit: add exec at the end of the script

Add an 'exec' at the end of the spark-submit script, to avoid keeping a
bash process hanging around while it runs.  This makes ps look a little
bit nicer.

Author: Colin Patrick Mccabe <cmccabe@cloudera.com>

Closes #858 from cmccabe/SPARK-1907 and squashes the following commits:

7023b64 [Colin Patrick Mccabe] spark-submit: add exec at the end of the script
[SPARK-1822] SchemaRDD.count() should use query optimizer

Author: Kan Zhang <kzhang@apache.org>

Closes #841 from kanzhang/SPARK-1822 and squashes the following commits:

2f8072a [Kan Zhang] [SPARK-1822] Minor style update
cf4baa4 [Kan Zhang] [SPARK-1822] Adding Scaladoc
e67c910 [Kan Zhang] [SPARK-1822] SchemaRDD.count() should use optimizer
Added PEP8 style configuration file.

This sets the max line length to 100 as a PEP8 exception.

Author: Reynold Xin <rxin@apache.org>

Closes #872 from rxin/pep8 and squashes the following commits:

2f26029 [Reynold Xin] Added PEP8 style configuration file.
SPARK-1822: Some minor cleanup work on SchemaRDD.count()

Minor cleanup following #841.

Author: Reynold Xin <rxin@apache.org>

Closes #868 from rxin/schema-count and squashes the following commits:

5442651 [Reynold Xin] SPARK-1822: Some minor cleanup work on SchemaRDD.count()
Added license header for tox.ini.

(cherry picked from commit fa541f32c5b92e6868a9c99cbb2c87115d624d23)
Signed-off-by: Reynold Xin <rxin@apache.org>
Fix PEP8 violations in examples/src/main/python.

Author: Reynold Xin <rxin@apache.org>

Closes #870 from rxin/examples-python-pep8 and squashes the following commits:

2829e84 [Reynold Xin] Fix PEP8 violations in examples/src/main/python.
Python docstring update for sql.py.

Mostly related to the following two rules in PEP8 and PEP257:
- Line length < 72 chars.
- First line should be a concise description of the function/class.

Author: Reynold Xin <rxin@apache.org>

Closes #869 from rxin/docstring-schemardd and squashes the following commits:

7cf0cbc [Reynold Xin] Updated sql.py for pep8 docstring.
0a4aef9 [Reynold Xin] Merge branch 'master' into docstring-schemardd
6678937 [Reynold Xin] Python docstring update for sql.py.
Fix PEP8 violations in Python mllib.

Author: Reynold Xin <rxin@apache.org>

Closes #871 from rxin/mllib-pep8 and squashes the following commits:

848416f [Reynold Xin] Fixed a typo in the previous cleanup (c -> sc).
a8db4cd [Reynold Xin] Fix PEP8 violations in Python mllib.
SPARK-1903 Document Spark's network connections

https://issues.apache.org/jira/browse/SPARK-1903

Author: Andrew Ash <andrew@andrewash.com>

Closes #856 from ash211/SPARK-1903 and squashes the following commits:

6e7782a [Andrew Ash] Add the technology used on each port
1d9b5d3 [Andrew Ash] Document port for history server
56193ee [Andrew Ash] spark.ui.port becomes worker.ui.port and master.ui.port
a774c07 [Andrew Ash] Wording in network section
90e8237 [Andrew Ash] Use real :toc instead of the hand-written one
edaa337 [Andrew Ash] Master -> Standalone Cluster Master
57e8869 [Andrew Ash] Port -> Default Port
3d4d289 [Andrew Ash] Title to title case
c7d42d9 [Andrew Ash] [WIP] SPARK-1903 Add initial port listing for documentation
a416ae9 [Andrew Ash] Word wrap to 100 lines
[SQL] Minor: Introduce SchemaRDD#aggregate() for simple aggregations

```scala
rdd.aggregate(Sum('val))
```
is just shorthand for

```scala
rdd.groupBy()(Sum('val))
```

but seems be more natural than doing a groupBy with no grouping expressions when you really just want an aggregation over all rows.

Did not add a JavaSchemaRDD or Python API, as these seem to be lacking several other methods like groupBy() already -- leaving that cleanup for future patches.

Author: Aaron Davidson <aaron@databricks.com>

Closes #874 from aarondav/schemardd and squashes the following commits:

e9e68ee [Aaron Davidson] Add comment
db6afe2 [Aaron Davidson] Introduce SchemaRDD#aggregate() for simple aggregations
HOTFIX: Add no-arg SparkContext constructor in Java

Self explanatory.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #878 from pwendell/java-constructor and squashes the following commits:

2cc1605 [Patrick Wendell] HOTFIX: Add no-arg SparkContext constructor in Java
[SPARK-1914] [SQL] Simplify CountFunction not to traverse to evaluate all child expressions.

`CountFunction` should count up only if the child's evaluated value is not null.

Because it traverses to evaluate all child expressions, even if the child is null, it counts up if one of the all children is not null.

Author: Takuya UESHIN <ueshin@happy-camper.st>

Closes #861 from ueshin/issues/SPARK-1914 and squashes the following commits:

3b37315 [Takuya UESHIN] Merge branch 'master' into issues/SPARK-1914
2afa238 [Takuya UESHIN] Simplify CountFunction not to traverse to evaluate all child expressions.
Fix scalastyle warnings in yarn alpha

Author: witgo <witgo@qq.com>

Closes #884 from witgo/scalastyle and squashes the following commits:

4b08ae4 [witgo] Fix scalastyle warnings in yarn alpha
SPARK-1925: Replace '&' with '&&'

JIRA: https://issues.apache.org/jira/browse/SPARK-1925

Author: zsxwing <zsxwing@gmail.com>

Closes #879 from zsxwing/SPARK-1925 and squashes the following commits:

5cf5a6d [zsxwing] SPARK-1925: Replace '&' with '&&'
[SPARK-1931] Reconstruct routing tables in Graph.partitionBy

905173df57b90f90ebafb22e43f55164445330e6 introduced a bug in partitionBy where, after repartitioning the edges, it reuses the VertexRDD without updating the routing tables to reflect the new edge layout. Subsequent accesses of the triplets contain nulls for many vertex properties.

This commit adds a test for this bug and fixes it by introducing `VertexRDD#withEdges` and calling it in `partitionBy`.

Author: Ankur Dave <ankurdave@gmail.com>

Closes #885 from ankurdave/SPARK-1931 and squashes the following commits:

3930cdd [Ankur Dave] Note how to set up VertexRDD for efficient joins
9bdbaa4 [Ankur Dave] [SPARK-1931] Reconstruct routing tables in Graph.partitionBy
SPARK-1929 DAGScheduler suspended by local task OOM

DAGScheduler does not handle local task OOM properly, and will wait for the job result forever.

Author: Zhen Peng <zhenpeng01@baidu.com>

Closes #883 from zhpengg/bugfix-dag-scheduler-oom and squashes the following commits:

76f7eda [Zhen Peng] remove redundant memory allocations
aa63161 [Zhen Peng] SPARK-1929 DAGScheduler suspended by local task OOM
Fixed the error message for OutOfMemoryError in DAGScheduler.