Find out wich External Storages work

[JonathanTreffler]

So far i have found these Storages that implement the fopen function:

• AmazonS3
• FTP
• SFTP
• SMB
• Swift

So these should theoretically work, but do they ?
I don't know and its hard to test since i don't use any of these external storages

[e-alfred]

I already put some information here: #91

As far as I tested SMB works, SFTP sometimes, Webdav times out (see #92), Openstack/Amazon S3/FTP are untested as of now.

We should show the error ID so people can easily find the log entry if their upload failed. Currently, it is hidden in the browser console inside the flow.js status messages.