Keep track of collapsed modules

We should keep track of the collapsed modules in de sidebar. This will come in handy when an unauthenticated user wants to continue adding series after being prompted to sign in.
![](http://vignette2.wikia.nocookie.net/halofanon/images/f/f5/Meme_-_O_RLY!.jpg/revision/latest?cb=20110323030349)

Make sense, forgot about that for a minute.