Store collectives folder for users in database

Instead of getting and translating the collectives user folder each time the filesystem is initialized, just do that the first time and store the folder path in database as a user setting.

This fixes issues with several collectives folders (in different languages) being created in the user home directory. Regardless of different clients with different languages, we now always use the folder path that's stored for the user in database.

It also should improve performance, as we no longer need to get the user language everytime we initialize the filesystem.

Fixes: #238 (closed), #275 (closed)

Screencasts

Without trash:

With trash: