Add `--rest` to `xst upload`

[line-o]

Enhancement

Allow uploads of files and folders using the RESTclient when the --rest option is set. Given the inefficiency in uploads we could make uploads via REST the default and only fallback to XML-RPC when REST is not available.

Justification

Uploading large files over XML-RPC can lead to a heap exception in nodeJS. This was reported by a user and I could reproduce a memory overhead of almost 4 times the size of a single large XML resource that I uploaded for testing.

The xst process needed 760 MB of RAM to upload a file with 200MB of XML.

Alternatives

I don't see an alternative. To be discussed.