quick_frontend (constants, quick_app, quick_contact_list): blogging refactoring (not finished):

- 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

frontends/src/quick_frontend/constants.py

@@ -61,6 +61,11 @@ class Const(constants.Const):
         "paused": u"⦷"
     }
 
+    # Blogs
+    ENTRY_MODE_TEXT = "text"
+    ENTRY_MODE_RICH = "rich"
+    ENTRY_MODE_XHTML = "xhtml"
+
     # Widgets management
     # FIXME: should be in quick_frontend.constant, but Libervia doesn't inherit from it
     WIDGET_NEW = 'NEW'