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/canalplus/pages/__init__.py

@@ -18,7 +18,6 @@
 # along with weboob. If not, see <http://www.gnu.org/licenses/>.
 
 from .initpage import InitPage
-from .video import CanalplusVideo
 from .videopage import VideoPage
 
-__all__ = ['InitPage', 'VideoPage',  'CanalplusVideo']
+__all__ = ['InitPage', 'VideoPage']