[SPARK-1644] The org.datanucleus:* should not be packaged into spark-assembly-*.jar

Author: witgo <witgo@qq.com>

Closes #688 from witgo/SPARK-1644 and squashes the following commits:

56ad6ac [witgo] review commit
87c03e4 [witgo] Merge branch 'master' of https://github.com/apache/spark into SPARK-1644
6ffa7e4 [witgo] review commit
a597414 [witgo] The org.datanucleus:* should not be packaged into spark-assembly-*.jar
[SQL] Upgrade parquet library.

I think we are hitting this issue in some perf tests: https://github.com/Parquet/parquet-mr/commit/6aed5288fd4a1398063a5a219b2ae4a9f71b02cf

Credit to @aarondav !

Author: Michael Armbrust <michael@databricks.com>

Closes #684 from marmbrus/upgradeParquet and squashes the following commits:

e10a619 [Michael Armbrust] Upgrade parquet library.
[SPARK-1778] [SQL] Add 'limit' transformation to SchemaRDD.

Add `limit` transformation to `SchemaRDD`.

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

Closes #711 from ueshin/issues/SPARK-1778 and squashes the following commits:

33169df [Takuya UESHIN] Add 'limit' transformation to SchemaRDD.
SPARK-1708. Add a ClassTag on Serializer and things that depend on it

This pull request contains a rebased patch from @heathermiller (https://github.com/heathermiller/spark/pull/1) to add ClassTags on Serializer and types that depend on it (Broadcast and AccumulableCollection). Putting these in the public API signatures now will allow us to use Scala Pickling for serialization down the line without breaking binary compatibility.

One question remaining is whether we also want them on Accumulator -- Accumulator is passed as part of a bigger Task or TaskResult object via the closure serializer so it doesn't seem super useful to add the ClassTag there. Broadcast and AccumulableCollection in contrast were being serialized directly.

CC @rxin, @pwendell, @heathermiller

Author: Matei Zaharia <matei@databricks.com>

Closes #700 from mateiz/spark-1708 and squashes the following commits:

1a3d8b0 [Matei Zaharia] Use fake ClassTag in Java
3b449ed [Matei Zaharia] test fix
2209a27 [Matei Zaharia] Code style fixes
9d48830 [Matei Zaharia] Add a ClassTag on Serializer and things that depend on it
fix broken in link in python docs

Author: Andy Konwinski <andykonwinski@gmail.com>

Closes #650 from andyk/python-docs-link-fix and squashes the following commits:

a1f9d51 [Andy Konwinski] fix broken in link in python docs
Add Python includes to path before depickling broadcast values

This fixes https://issues.apache.org/jira/browse/SPARK-1731 by adding the Python includes to the PYTHONPATH before depickling the broadcast values

@airhorns

Author: Bouke van der Bijl <boukevanderbijl@gmail.com>

Closes #656 from bouk/python-includes-before-broadcast and squashes the following commits:

7b0dfe4 [Bouke van der Bijl] Add Python includes to path before depickling broadcast values