Python call for s3filecopy

A call on the R client to run an s3 file copy to a customer bucket.
Arguments: list of file entity ids, name of bucket to copy to, overwrite true/false
Returns list of statuses for each file, error status ERROR with description or status UPTODATE/COPIED for success

Rest commands:

token <- synRestPOST("/file/s3FileCopy/async/start", list(
concreteType="org.sagebionetworks.repo.model.file.S3FileCopyRequest",
files=list("syn3916345"),
bucket="test-requester-pays-copy.sagebionetworks.org",
overwrite=T), endpoint=synapseFileServiceEndpoint())
synRestGET(sprintf("/file/s3FileCopy/async/get/%s", token), endpoint=synapseFileServiceEndpoint())