this patch add a parameter to ModuleFinder, to not
recurse when searching module.
This way, someone can compute the modules needed by a
specific file, without having to compute all other
imported module, which may take time for result that
are no t needed. 

With the current system, you cannot create a clean
graph of modules dependancy, since  they are all on the
same level.

This patch do not change the default behavior.