- adaptation to backend modifications
- moved common blogging parts from Libervia to quick frontend
- QuickApp use a MB_HANDLE class variable to indicated if blogging is managed by the frontend (and avoid waste of resources if not)
- comments are now managed inside parent entry, as a result a tree of comments is now possible
- Entry.level indicate where in the tree we are (-1 mean parent QuickBlog, 0 mean main item, more means comment)
- items + comments are requested in 1 shot, and RTDeferred are used to avoid blocking while waiting for them
- in QuickBlog, id2entries allow to get Entry from it's item id, and node2entries allow to get Entry(ies) hosting a comments node
- QuickBlog.new_message_target tell where a new message will be sent by default
