Add user and permissions to the File Module

[fgeorges]

The File Module does not have any function to read nor write common file properties, like the owner/group of a file, or the permission bits (read/write/execute). Some of those concepts might be tight to a specific platform, but some might be generalized. Even if it is not possible in a totally generic way, it would be interesting still to provide such tools.

Maybe some equivalent APIs for other languages might be of inspiration.

But definitely for the next version of the module, probably 1.1 :-)