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/components/chat/EventContent.qml

@@ -11,7 +11,7 @@ RowLayout {
     anchors.right: isOwn ? parent.right : undefined
 
     readonly property string contentText:
-        isMessage ?  "" : ChatJS.get_event_text(type, dict)
+        isMessage ?  "" : ChatJS.getEventText(type, dict)
 
     Base.Avatar {
         id: avatar
@@ -26,7 +26,7 @@ RowLayout {
               (isUndecryptableEvent ? "darkred" : "gray") + "'>" +
               (displayName.value || dict.sender) + " " + contentText +
               "&nbsp;&nbsp;<font size=" + smallSize + "px color='gray'>" +
-              Qt.formatDateTime(date_time, "hh:mm:ss") +
+              Qt.formatDateTime(dateTime, "hh:mm:ss") +
               "</font></font>"
         textFormat: Text.RichText
         background: Rectangle {color: "#DDD"}