Identify correctly the mediawiki files even if the File: namespace is translated

In media wiki, the namespaces can be translated, including the "File" namespace which is the standard namespace for media wiki files (consider, for the sake of this issue, the french equivalent, "Fichier").
This has two consequences:

• in the media wiki dump, the file pages will appear prefixed by Fichier: instead of File:. The importer needs to identify those files correctly (applies to the case when the files are not attached during the import)
• in the media wiki pages, in the syntax, both [[File:..]] and [[Fichier:..]] syntaxes will work and do the same thing: make a link to a file or display an image if the file in question is an image. [[Fichier:..]] syntax also needs to be identified as a file (currently not the case, only [[File:..]] works).