Add direct uploads to S3 assetstore in python client

[Doreapp]

Description: Currently, python client does not check the assetstore type before uploading a file. It uses POST /file and POST /file/chunk routes, without caring about returned behavior field from POST /file request.

Suggestion: Python client (as well as related CLI), should handle behavior field, as done in FileModel.js. When encountering s3 behavior, it should upload files directly to S3 instance, as S3UploadHandle.js does.