[SPARK-4896] don’t redundantly overwrite executor JAR deps

Author: Ryan Williams <ryan.blake.williams@gmail.com>

Closes #2848 from ryan-williams/fetch-file and squashes the following commits:

c14daff [Ryan Williams] Fix copy that was changed to a move inadvertently
8e39c16 [Ryan Williams] code review feedback
788ed41 [Ryan Williams] don’t redundantly overwrite executor JAR deps

(cherry picked from commit 7981f969762e77f1752ef8f86c546d4fc32a1a4f)
Signed-off-by: Josh Rosen <joshrosen@databricks.com>

Conflicts:
	core/src/main/scala/org/apache/spark/util/Utils.scala
SPARK-2641: Passing num executors to spark arguments from properties file

Since we can set spark executor memory and executor cores using property file, we must also be allowed to set the executor instances.

Author: Kanwaljit Singh <kanwaljit.singh@guavus.com>

Closes #1657 from kjsingh/branch-1.0 and squashes the following commits:

d8a5a12 [Kanwaljit Singh] SPARK-2641: Fixing how spark arguments are loaded from properties file for num executors

Conflicts:
	core/src/main/scala/org/apache/spark/deploy/SparkSubmitArguments.scala
[Minor] Build Failed: value defaultProperties not found

Mvn Build Failed: value defaultProperties not found .Maybe related to this pr:
https://github.com/apache/spark/commit/1d648123a77bbcd9b7a34cc0d66c14fa85edfecd
andrewor14 can you look at this problem?

Author: huangzhaowei <carlmartinmax@gmail.com>

Closes #3749 from SaintBacchus/Mvn-Build-Fail and squashes the following commits:

8e2917c [huangzhaowei] Build Failed: value defaultProperties not found

(cherry picked from commit a764960b3b6d842eef7fa4777c8fa99d3f60fa1e)
Signed-off-by: Josh Rosen <joshrosen@databricks.com>