[SPARK-9180] fix spark-shell to accept --name option

This patch fixes [[SPARK-9180]](https://issues.apache.org/jira/browse/SPARK-9180).
Users can now set the app name of spark-shell using `spark-shell --name "whatever"`.

Author: Kenichi Maehashi <webmaster@kenichimaehashi.com>

Closes #7512 from kmaehashi/fix-spark-shell-app-name and squashes the following commits:

e24991a [Kenichi Maehashi] use setIfMissing instead of setAppName
18aa4ad [Kenichi Maehashi] fix spark-shell to accept --name option

bin/spark-shell

@@ -47,11 +47,11 @@ function main() {
     # (see https://github.com/sbt/sbt/issues/562).
     stty -icanon min 1 -echo > /dev/null 2>&1
     export SPARK_SUBMIT_OPTS="$SPARK_SUBMIT_OPTS -Djline.terminal=unix"
-    "$FWDIR"/bin/spark-submit --class org.apache.spark.repl.Main "$@"
+    "$FWDIR"/bin/spark-submit --class org.apache.spark.repl.Main --name "Spark shell" "$@"
     stty icanon echo > /dev/null 2>&1
   else
     export SPARK_SUBMIT_OPTS
-    "$FWDIR"/bin/spark-submit --class org.apache.spark.repl.Main "$@"
+    "$FWDIR"/bin/spark-submit --class org.apache.spark.repl.Main --name "Spark shell" "$@"
   fi
 }
 

bin/spark-shell2.cmd

@@ -32,4 +32,4 @@ if "x%SPARK_SUBMIT_OPTS%"=="x" (
 set SPARK_SUBMIT_OPTS="%SPARK_SUBMIT_OPTS% -Dscala.usejavacp=true"
 
 :run_shell
-%SPARK_HOME%\bin\spark-submit2.cmd --class org.apache.spark.repl.Main %*
+%SPARK_HOME%\bin\spark-submit2.cmd --class org.apache.spark.repl.Main --name "Spark shell" %*

repl/scala-2.10/src/main/scala/org/apache/spark/repl/SparkILoop.scala

@@ -1008,9 +1008,9 @@ class SparkILoop(
     val jars = SparkILoop.getAddedJars
     val conf = new SparkConf()
       .setMaster(getMaster())
-      .setAppName("Spark shell")
       .setJars(jars)
       .set("spark.repl.class.uri", intp.classServerUri)
+      .setIfMissing("spark.app.name", "Spark shell")
     if (execUri != null) {
       conf.set("spark.executor.uri", execUri)
     }

repl/scala-2.11/src/main/scala/org/apache/spark/repl/Main.scala

@@ -65,9 +65,9 @@ object Main extends Logging {
     val jars = getAddedJars
     val conf = new SparkConf()
       .setMaster(getMaster)
-      .setAppName("Spark shell")
       .setJars(jars)
       .set("spark.repl.class.uri", classServer.uri)
+      .setIfMissing("spark.app.name", "Spark shell")
     logInfo("Spark class server started at " + classServer.uri)
     if (execUri != null) {
       conf.set("spark.executor.uri", execUri)