add s3_get module for ONLY get a file from S3 and set attributes (owner/group/mode...) same as file module.

I usually use "s3" module for get file from S3.
I want to set attributes (owner/group/mode) of downloaded file,
first I tried to modify s3 module, but there is already "mode" option for another purpose.
( "mode" means operation like put/get/geturl etc. )

So I made a new module "s3_get" to ONLY get a file from S3 and set attributes of a downloaded file.