Soliman

Allow to customize timestamp format

1

### Feature/improvement The timestamp used for subfolder creation is always `timestamp.format('YYYY-MM-DD-HH-mm-ss')` It would be better to have a parameter to customize this behaviour. The best would be to have the...

### PR checklist - [x] Read the [contribution guidelines](https://github.com/swagger-api/swagger-codegen/blob/master/CONTRIBUTING.md). - [x] Ran the shell script under `./bin/` to update Petstore sample so that CIs can verify the change. (For instance,...