This allows us to abandon our own additional config parameters for
aws cloud(like region) and use the ones from .aws/config by default.
Plus, boto3 automatically switches to multipartupload if file is bigger
than a certain limit, allowing us to remove a lot of our own code.
Fixes#650Fixes#636Fixes#601
Signed-off-by: Ruslan Kuprieiev <[email protected]>