Permissioned downloads for files

[rayokamoto]

Sometimes, you might not want other users downloading files that they do not own. As such, a user should be able to set a file as only downloadable by themselves.

Very important to note that this DOES NOT replace encrypting files before uploading and that users should encrypt their files if they want true security of their data.

With that being said, a future client-facing Storb CLI could feature an option to automatically encrypt the file before uploading.