Capitalization, list model and room header work

- Standardized capitalization for variables and file names everywhere in
  QML and JS, get rid of mixed camelCase/snakeCase,
  use camelCase like everywhere in Qt

- ListModel items are now stored and returned as real QObjects with
  PyQt properties and signals.
  This makes dynamic property binding a lot easier and eliminates the need
  for many hacks.

- New update(), updateOrAppendWhere() methods and roles property
  for ListModel

- RoomHeader now properly updates when the room title or topic changes

- Add Backend.pdb(), to make it easier to start the debugger from QML

harmonyqml/backend/model/__init__.py

@@ -1,7 +1,7 @@
 # Copyright 2019 miruka
 # This file is part of harmonyqml, licensed under GPLv3.
 
+from . import items
 from .list_model import ListModel
 from .list_model_map import ListModelMap
 from .qml_models import QMLModels
-from . import enums, items