Uploadable: Private files

[silverbackdan]

Need to add tests for using Amazon S3 with private files to check how it is handled. Perhaps a temporary token is generated which expires shortly afterwards... I hope! If not, then we need to ensure it acts in this way.

For the actual uploaded file (not imagine) we will be hitting an endpoint for the given resource. This means an application developer can hook into events to prevent access to the resource and therefore prevent access to the download....

Maybe address in alpha...