Fixes for swift4 language (#6116)

* Fix build error in Xcode 9 beta 3, as .compact is no longer defined

* Add test schema for Swift 4 and associated script and config files

* Add test app for swift4Test.json schema

* Make integer, Integer, int, and Int32 types map to Swift Int type instead of Int32 type

* Add CodingKeys to model template, which allows us to serialize/deserialize variable names that are different than property names

* Make updates to Swift 4 test schema

* Fixes for unit test app for swift4Test.json Swift 4 test schema

bin/swift4-test.sh

@@ -0,0 +1,31 @@
+#!/bin/sh
+
+SCRIPT="$0"
+
+while [ -h "$SCRIPT" ] ; do
+  ls=`ls -ld "$SCRIPT"`
+  link=`expr "$ls" : '.*-> \(.*\)$'`
+  if expr "$link" : '/.*' > /dev/null; then
+    SCRIPT="$link"
+  else
+    SCRIPT=`dirname "$SCRIPT"`/"$link"
+  fi
+done
+
+if [ ! -d "${APP_DIR}" ]; then
+  APP_DIR=`dirname "$SCRIPT"`/..
+  APP_DIR=`cd "${APP_DIR}"; pwd`
+fi
+
+executable="./modules/swagger-codegen-cli/target/swagger-codegen-cli.jar"
+
+if [ ! -f "$executable" ]
+then
+  mvn clean package
+fi
+
+# if you've executed sbt assembly previously it will use that instead.
+export JAVA_OPTS="${JAVA_OPTS} -XX:MaxPermSize=256M -Xmx1024M -DloggerPath=conf/log4j.properties"
+ags="$@ generate -t modules/swagger-codegen/src/main/resources/swift4 -i modules/swagger-codegen/src/test/resources/2_0/swift4Test.json -l swift4 -c ./bin/swift4-test.json -o samples/client/test/swift4/default"
+
+java $JAVA_OPTS -jar $executable $ags