Make CapCollection understandable and useable by humans

* Make the declaration of fct and it in the constructor Collection,
 instead of adding them from the outside
* Add a function to flatten a list containing collection (solves the
 radioob search crash)
* Better display of collections in the "ls" command (and display both id
 and title)
* The "cd" command goes to the root of the path (like the UNIX cd)
* Move the Video object of canalplus in a correct path
* Make Collection iterable
* Add comments to CapCollection
* Cache the result of fct in a Collection; it is only called once
* CollectionNotFound errors can be more explicit by providing a path
* Require utf-8 in collection paths
* Code cleanups

modules/nova/backend.py

@@ -64,7 +64,7 @@ class NovaBackend(BaseBackend, ICapRadio, ICapCollection):
 
     def iter_resources(self, split_path):
         if len(split_path) > 0:
-            raise CollectionNotFound()
+            raise CollectionNotFound(split_path)
 
         for id in self._RADIOS.iterkeys():
             yield self.get_radio(id)