Identify category markers even if the Category: namespace is translated

In media wiki, the standard namespaces can be translated, for example, in french, the standard "Category" namespace can become "Catégorie".

This allows the category markers (that are currently ignored, until MEDIAWIKI-52 is fixed), to be written in 2 ways, in the same wiki instance and even in the same page, either [[Category:MyCat]] or [[Catégorie:MyCat]] will mark the page as being part of MyCat. The importer needs to handle both these syntaxes the same, which is currently not the case (only "Category" is currently identified as a category).