They bring nothing of value (we never use import * anyway) and introduce
a maintenance burden.
The __all__ that I left might not be very useful either but at least
they are not a pain to maintain; they are also used by pyflakes in some
cases.
One of the goal is to not import all modules needed by filters by
loading the page file.
In the same goal, move the import of parsers in the class definition.
There is now a "latest" collection (or "latest_nsfw").
The feature didn't look much used, since it didn't work on many
backends.
Using collections will make it easy to support other things
like most viewed, featured, etc.
As a bonus, I added tests for every backend with the feature.
I used autopep8 on some files and did carefully check the changes.
I ignored E501,E302,E231,E225,E222,E221,E241,E203 in my search, and at
least E501 on any autopep8 run.
Other style fixes not related to PEP8:
* Only use new-style classes. I don't think the usage of old-style
classes was voluntary. Old-style classes are removed in Python 3.
* Convert an if/else to a one-liner in mediawiki, change docstring style
change to a comment something that wasn't really appropriate for a
docstring.
* Unneeded first if condition in meteofrance
