[SPARK-2295] [SQL] Make JavaBeans nullability stricter.

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

Closes #1235 from ueshin/issues/SPARK-2295 and squashes the following commits:

201c508 [Takuya UESHIN] Make JavaBeans nullability stricter.
[SPARK-2286][UI] Report exception/errors for failed tasks that are not ExceptionFailure

Also added inline doc for each TaskEndReason.

Author: Reynold Xin <rxin@apache.org>

Closes #1225 from rxin/SPARK-2286 and squashes the following commits:

6a7959d [Reynold Xin] Fix unit test failure.
cf9d5eb [Reynold Xin] Merge branch 'master' into SPARK-2286
a61fae1 [Reynold Xin] Move to line above ...
38c7391 [Reynold Xin] [SPARK-2286][UI] Report exception/errors for failed tasks that are not ExceptionFailure.
Fixing AWS instance type information based upon current EC2 data

Fixed a problem in previous file in which some information regarding AWS instance types were wrong. Such information was updated base upon current AWS EC2 data.

Author: Zichuan Ye <jerry@tangentds.com>

Closes #1156 from jerry86/master and squashes the following commits:

ff36e95 [Zichuan Ye] Fixing AWS instance type information based upon current EC2 data
Strip '@' symbols when merging pull requests.

Currently all of the commits with 'X' in them cause person X to
receive e-mails every time someone makes a public fork of Spark.

marmbrus who requested this.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #1239 from pwendell/strip and squashes the following commits:

22e5a97 [Patrick Wendell] Strip '@' symbols when merging pull requests.