[PowerShell] Add PowerShell API client generator (WIP) (#5789)

* add powershell generator (wip)

* minor fix to api template

* rename model files

* Powershell generator fix (#11)

* Fix typo

pacakge -> package

* Add missing `petstore` subfolder to $ClientPath

* Resolve $ClientPath to absolute path

Start-Process needs WorkingDirectory to be absolute

* Fix spaces in variable name

${ somevar } is a vairable that literally has spaces in name. We need to
temporarily redifine mustache delimiters so we can generate var. names
without spaces.

* Fix typo

Remove stray `r`

* Fix *.ps1 import in module

Directory structure has changed + we should export functions using
manifest.

* Remove erroneous file

* various fixes and enhancements

* remove nullable for string

* change function name based on feedback by beatcracker

* set index to start at 0

* fix file type

* Powershell generator fix 1 (#12)

* Add closing curly brace

* Fix duplicated '['

* Get FunctionsToExport using AST

Discussion: #5789

* add guid option to powershell generator

* add test files, remove docs

* fix array of items

* clean up powershell comment, update model/api test files

bin/powershell-petstore.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/powershell -i modules/swagger-codegen/src/test/resources/2_0/petstore.yaml -l powershell -o samples/client/petstore/powershell_test --additional-properties packageGuid=a27b908d-2a20-467f-bc32-af6f3a654ac5 $@"
+
+java ${JAVA_OPTS} -jar ${executable} ${ags}

bin/windows/powershell-petsstore.bat

@@ -0,0 +1,10 @@
+set executable=.\modules\swagger-codegen-cli\target\swagger-codegen-cli.jar
+
+If Not Exist %executable% (
+  mvn clean package
+)
+
+REM set JAVA_OPTS=%JAVA_OPTS% -Xmx1024M -DloggerPath=conf/log4j.properties
+set ags=generate  -i modules\swagger-codegen\src\test\resources\2_0\petstore.yaml -l powershell -o samples\client\petstore\powershell
+
+java %JAVA_OPTS% -jar %executable% %ags%