Add auto-generated test files

[wing328]

As part of #1921, we've add capabilities to generate test files for API and model files.

If anyone has cycle to add the feature to the following languages, please reply to let us know:

• Android
• Bash
• C++
• C# ([C#] Add unit tests for C# APIs and models #2007)
• Clojure
• Dart
• Elixir
• Flash
• Go (issue #1948, added testing code to test go api #2532, issue #2569: added model tests for Go #2577)
• Groovy
• Javascript
• Java
• ObjC
• Perl ([Perl] generate files for unit testing models and API files #2109)
• PHP ([PHP] generate files for unit testing models and API files #1921)
• Python
• Ruby ([Ruby] add auto-generated test cases (rspec) #1980)
• Swift
• Scala
• TypeScript

Keywords: unit tests, integration tests