[SPARK-3463] [PySpark] aggregate and show spilled bytes in Python

Aggregate the number of bytes spilled into disks during aggregation or sorting, show them in Web UI.

![spilled](https://cloud.githubusercontent.com/assets/40902/4209758/4b995562-386d-11e4-97c1-8e838ee1d4e3.png)

This patch is blocked by SPARK-3465. (It includes a fix for that).

Author: Davies Liu <davies.liu@gmail.com>

Closes #2336 from davies/metrics and squashes the following commits:

e37df38 [Davies Liu] remove outdated comments
1245eb7 [Davies Liu] remove the temporary fix
ebd2f43 [Davies Liu] Merge branch 'master' into metrics
7e4ad04 [Davies Liu] Merge branch 'master' into metrics
fbe9029 [Davies Liu] show spilled bytes in Python in web ui
SPARK-3039: Allow spark to be built using avro-mapred for hadoop2

SPARK-3039: Adds the maven property "avro.mapred.classifier" to build spark-assembly with avro-mapred with support for the new Hadoop API. Sets this property to hadoop2 for Hadoop 2 profiles.

I am not very familiar with maven, nor do I know whether this potentially breaks something in the hive part of spark. There might be a more elegant way of doing this.

Author: Bertrand Bossy <bertrandbossy@gmail.com>

Closes #1945 from bbossy/SPARK-3039 and squashes the following commits:

c32ce59 [Bertrand Bossy] SPARK-3039: Allow spark to be built using avro-mapred for hadoop2
[SPARK-3452] Maven build should skip publishing artifacts people shouldn...

...'t depend on

Publish local in maven term is `install`

and publish otherwise is `deploy`

So disabled both for following projects.

Author: Prashant Sharma <prashant.s@imaginea.com>

Closes #2329 from ScrapCodes/SPARK-3452/maven-skip-install and squashes the following commits:

257b79a [Prashant Sharma] [SPARK-3452] Maven build should skip publishing artifacts people shouldn't depend on
Merge branch 'master' of git://git.apache.org/spark into json-exposing-feature