Create language-specified base class

Description

As the awesome Swagger Codegen community adds more generators (e.g clients, servers) to Swagger Codegen, we want to refactor some generators to create language-specific base class so as to reuse the code that are common to generators for the same langauges. Here are a few examples

C++ C# Java Typescript

Here is a list to track progress:

• Android
• Bash
• C++
• C#
• Clojure
• Dart
• Elixir
• Eiffel
• Flash
• Go (https://github.com/swagger-api/swagger-codegen/pull/7197)
• Groovy
• Javascript
• Java
• ObjC
• Perl
• PHP
• PowerShell
• Python
• Ruby
• Swift
• Scala
• TypeScript

Swagger-codegen version

Latest master

Suggest a Fix/Enhancement

If anyone wants to work on the base class creation, please reply to let us know.