Add File permission give every users a way to add file in any other user area

[gbastien]

As the "Add File" permission is given on every user personal plonemeeting area to the role "Member", every member of the site can add a file in any plonemeeting area of other users... This is caused when we give thsi permission to the config.py/ploneMeetingUpdaters list of roles. Check if we can remove "Member" from this list... Check if it would not be usefull to turn a Meeting into a Folder and to store the generated podtemplates_to_file ATFile instances into it...