i18n support for "file" node type

Issue Summary

File Framework handles files as nodes, which gives extensive possibilities manage them.

This implies of course that a "file" node corresponds to one and only one file.

Regarding i18n, one could think that FF is not concerned about as the node should be language neutral or should follow the file language.

However,
- many files don't have inherent language (pictures, a large part of music)
- it can be useful to display the information about a file in different languages regardless the content itself

This can be done by attaching the file by its node to another "informative' node, but
- this is overkilling,
- File Browser and File Gallery have no longer purpose.

Great module again