add config.json in tiddlers folder for popupUri and folders tree

[bourgeoa]

Try to make the tiddlywiki multi-users and multi-podFolders

add a config.json with :

• popupUri
• all folderUrls pertaining to one tiddlywiki of a group of users (one per userPod)
  • each user folderPod shall retain his own tiddlers with write access to the other users or not
  • this implies that each tiddler has a source field (inside tiddlywiki)
  • there still is the conflict on writing, see if draft.of can be used