SPARK-2481: The environment variables SPARK_HISTORY_OPTS is covered in spark-env.sh

Author: witgo <witgo@qq.com>
Author: GuoQiang Li <witgo@qq.com>

Closes #1341 from witgo/history_env and squashes the following commits:

b4fd9f8 [GuoQiang Li] review commit
0ebe401 [witgo] *-history-server.sh load spark-config.sh
[SPARK-2976] Replace tabs with spaces

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

Closes #1895 from sarutak/SPARK-2976 and squashes the following commits:

1cf7e69 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into SPARK-2976
d1e0666 [Kousuke Saruta] Modified styles
c5e80a4 [Kousuke Saruta] Remove tab from JavaPageRank.java and JavaKinesisWordCountASL.java
c003b36 [Kousuke Saruta] Removed tab from sorttable.js