Add credentials support to Data spaces

[fviale]

• when resolving a file, it is possible to add user credentials
• these credentials can be used by the underlying apache VFS providers to perform authentication on the file system.
• Please note that the file:// VFS provider does not support authentication (becase the file provider is not able to perform impersonation). So at the moment only sftp (and possibly samba) support it. See https://commons.apache.org/proper/commons-vfs/filesystems.html
• This modification is the first part of the implementation to allow dataspace impersonation, the second part will be in the scheduling project (and the change is much bigger).