Fix arguments number for internal links

Each internal SIOC link (defined with rdfs:seeAlso + rdf:resource) should get the same number of args.

With the current exporter, when trying to scrap a SIOC-ed site:
- scrapping http://foobar/?q=sioc/blog/16 creates a file named "16"
- then, "" tries to create 16/1 file but can't as 16 is a file and not a folder.

I first thaught it was a scrapper issue but I think this is the role of the plugin to create nice URI/filenames.