Release v13.1.3 - #2454

* Added an annotations extension template at controller class level

* Add BasePath override config option for C# Controller.

To separate config from code-gen, a base path config variable is added so the base path can be overridden.

This can be useful when:

  - You have a virtual directory that you don't want in your routes.

  - You have a difference in the paths of your environments.

* Add BasePath override config option for C# Controller.

Change BasePath evalutation to use string.IsNullOrEmpty.

* Add BasePath override config option for C# Controller.

Change BasePath evalutation to use string.IsNullOrEmpty.

…such attribute is not set explicitly (#2381)

* OperationTagsProcessor processes OpenApiTagsAttribute and OpenApiTagAttribute  set for the class if they were not specified for method.

* Added OperationTagsProcessor tests

* Set VS version back to 16 in solution files