... size

Ways to set Application Master's memory on yarn-client mode:
1.  `spark.yarn.am.memory` in SparkConf or System Properties
2.  default value 512m

Note: this arguments is only available in yarn-client mode.

Author: WangTaoTheTonic <barneystinson@aliyun.com>

Closes #3607 from WangTaoTheTonic/SPARK4181 and squashes the following commits:

d5ceb1b [WangTaoTheTonic] spark.driver.memeory is used in both modes
6c1b264 [WangTaoTheTonic] rebase
b8410c0 [WangTaoTheTonic] minor optiminzation
ddcd592 [WangTaoTheTonic] fix the bug produced in rebase and some improvements
3bf70cc [WangTaoTheTonic] rebase and give proper hint
987b99d [WangTaoTheTonic] disable --driver-memory in client mode
2b27928 [WangTaoTheTonic] inaccurate description
b7acbb2 [WangTaoTheTonic] incorrect method invoked
2557c5e [WangTaoTheTonic] missing a single blank
42075b0 [WangTaoTheTonic] arrange the args and warn logging
69c7dba [WangTaoTheTonic] rebase
1960d16 [WangTaoTheTonic] fix wrong comment
7fa9e2e [WangTaoTheTonic] log a warning
f6bee0e [WangTaoTheTonic] docs issue
d619996 [WangTaoTheTonic] Merge branch 'master' into SPARK4181
b09c309 [WangTaoTheTonic] use code format
ab16bb5 [WangTaoTheTonic] fix bug and add comments
44e48c2 [WangTaoTheTonic] minor fix
6fd13e1 [WangTaoTheTonic] add overhead mem and remove some configs
0566bb8 [WangTaoTheTonic] yarn client mode Application Master memory size is same as driver memory size